Erik Schmidt's answer is probably the better one to go with (as it'll help you find the root cause), but I'll contribute a bit based on what I see from your description.
From your description, you have a player who enjoys:
And who doesn't enjoy:
And yet, this player is playing in a campaign that is low combat, high intrigue, and where the penalties for building a new character are incredibly prohibitive.
When players are marginalized, they tend to try to get into the spotlight in any way that they can. And that leads to disruptive behavior.
This leaves you with a few choices:
Try to get the player into a campaign that they'd enjoy (either by running an additional campaign, or by encouraging them to find/create a new group).
Remove the player from your campaign.
Find ways to compromise, attempting to bring your campaign and the problem player closer together.
The important thing to realize is that there is no way to force the player to like playing the way you and your other friends are playing.
Character Jumping
Some people like to play the same character, and enjoy the process of growing and developing that character. Other players prefer the creation process, authoring new characters and mechanical combinations.
Dealing with the first sort of player is pretty easy. That's traditional, long-form writing. We see examples of it all the time in many different forms of fiction.
The second sort of player, the one you have now, is a bit harder to deal with. Here are a few things I've picked up to help deal with that:
Avoid introductions
Either introduce the character during downtime ("And so the party rested for six months, and met a new companion"), or use the "poof" method ("of course I've always been a catfolk fighter. Human wizard? Ridiculous."). You want to avoid having players stuck constantly in the untrustworthy rookie slot.
Maintain player parity
New characters should be (or quickly become) the equals of established characters. It's no fun being the one guy who doesn't have an artifact.
The rule of thumb is that anything that's relevant frequently, whether it's powerful mechanically or narratively. A new character can probably be allowed to do without a one-time favor from a noble. But they should probably get written into a life-debt from the king of the current kingdom (or be given something else).
If the new character doesn't start with this stuff, then the stated goal should be to catch them up quickly (within a few sessions).
A level penalty is right out, unless it's a temporary one (or you're playing a game where levels aren't super important). For example, in my 7th Sea campaign, new characters start slightly below the lowest player. But all players are brought to the same experience total periodically.
Let them know that they won't get some of the depth other characters do, but make an effort anyway
From a DM's standpoint, the hardest thing about a character jumper is that you can't be sure of who they will be in the future. So if it takes you three months to author a storyline featuring that character, and they change characters every two, that creates an obvious conflict.
Let the player know about this, and give them an opportunity to work with you. And make an effort to work their current character into the plot from time to time anyway, as a show of good faith.
Combat and Intrigue
It sounds like this player enjoys combat quite a bit. Most likely, it's a chance to see how the mechanics of their character work, and to show off a little bit. This is all fine, except when it stomps all over the intrigue that other players want.
Give them combat
The easy answer here, is to make sure you're providing combat. Don't make talking the ultimate super-power. Give him a mixture of fodder that he can easily crush, and challenging mechanical opponents.
This is where the bit about parity and artifacts above becomes important. If their well-honed killing machine is constantly shown up by the senior characters with artifacts, the combat probably won't scratch their itch for them.
Signal shifts to intrigue mode
Provide clear signals to the group when a shift to intrigue mode is happening. Set intrigue in populated areas (cities, etc.) and combat outside of it. Have combat-based foes rush the group, snarling (or ambush them with a poisoned blade), while intrigue-based foes sit calmly on their thrones.
If nothing else, the occasional reminder that "Baron VonEvil is pretty well connected. Are you sure you want to fireball his face?" can help quite a bit.
Always have a backup plan
This player is going to blow stuff up. As the person who's planning things, that should be a possibility that you consider. How do you keep the plot moving if the villain doesn't get a chance to monologue? What happens if the whole room is fireballed?
The goal isn't to always have a way for the PCs to succeed per se, but simply for the story to always have a way forward. Perhaps that means that a scheme of the late baron crops up shortly after the heroes fail to find the documents, and now they have a fresh chance to investigate.
Or perhaps the important documents were partially sheltered by the lockbox they were in. They've been badly charred, but there's enough there to make out a new location to investigate. Is it a trap? Of course it's a trap. They're going in blind.
Communication
Talk to your players. Not just about how you want them to behave, but about what you're trying to do, and how you're trying to shape the campaign to the individual players. Make it a dialogue, and solicit their feedback.
I'm trying to add in some more interesting "boss fights." What did you think of that last one?
I really liked the way you guys managed to outsmart Baron VonEvil. That's given me some interesting options for the next couple of adventures.
My goal is to tell an epic story of your rise to power. I think we could use a bit more of the political stuff, I just need to work out how to write that.
Etc.
Recommended Reading
There are two excellent sections in roleplaying books that I'd highly recommend for dealing with this problem, if you can get your hands on them.
The first is for the entire group. It's located in the 7th Sea Players' Guide, on page 238 under the heading Resisting the Story.
It's a couple pages long, so I won't reproduce the entire thing here. But the representative part of it is this:
Don't poison the PC pool. Don't act destructively just because "it's in your character," and don't force other players either to ignore your action or kill your character because it's in their characters. Know where the line is and make sure you -- and your Hero -- never cross it.
This doesn't mean that there shouldn't be any conflict within your party. On the contrary, some of the best and most rewarding roleplaying experiences come from moral or ethical disputes between Heroes. As long as you know where the limits are, and when engaging conflict becomes irreconcilable conflict, feel free to pursue arguments with your fellow Heroes.
The Rich Burlew essay Making the Tough Decisions is another valuable discussion of this principle.
The second is for the DM. It's located in the 4th Edition Dungeons & Dragons Dungeon Masters' Guide (pages 8 through 10). It's a breakdown of the different kinds of players, why they come to the table, and how a DM can target each one.
Summary
This is a lot of text, and only really brushes on a lot of important topics. The core assumption here is that you would rather play with this player, than necessarily play your campaign as it exists now.
The key is to give the problem player things that they enjoy. With good communication, a willingness to tune your campaign to the players, and a bit of compromise, the problem player may become a lot more tractable when their needs are met.
There are a number of reasons why the character's book knowledge may not be useful at a given time. There are also a number of reasons why the character's knowledge wouldn't be as extensive as your player seems to think.
1) Book knowledge isn't practical experience.
You can read all the books in the world about riding a bicycle, and you'll still fall off the first time you actually try to do it. There's tons of sensory information that simply can't be reduced to words and absorbed, to say nothing of muscle memory.
2) Fantasy settings are not usually full of technical manuals.
There are no printing presses; everything is written by hand. Nobody writes a book explaining the basics of sailing, because that would be a massive waste of effort; it would be far easier to teach people how to sail by actually taking them sailing. This is especially true for things that are basic day-to-day skills for a decent segment of the population. Why would you write a book about how to do X when everyone you know already knows how? Books that include the application of these skills will usually be journals, and will either gloss over the details so no knowledge is necessary, or simply use sufficient explanation for someone who already knows how to understand what is being described.
3) Information in books may be highly localized to a specific place and/or time.
Knowing exactly how kayaks are built & operated by the jungle tribes in the distant land of Gobbeldey-gook doesn't help you operate a Gibberese catamaran. Knowing how ancient Gibberese oared catamarans were built & operated doesn't help you operate a modern Gibberese triple-masted caravel. Any books a centuries-old elf has read are likely to be tens, hundreds, or even thousands of years old, and has a higher chance of being out of date than the elf might realize.
4) Information in books may be straight up wrong.
Unless the book was written or dictated by a major deity whose portfolio includes honesty, its source is capable of deliberately lying, being factually incorrect, or both. History books in particular have a high risk of being revisionist, potentially to the point of being a complete whitewash. The idea that historians should faithfully record what actually happened, regardless of who it makes look bad, is pretty much limited to modern liberal democracies; in a fantasy setting writing a history book that doesn't flatter everyone powerful in the area is a good way to get a visit from some soldiers, assassins, or "adventurers".
5) Not every book is in Elven.
There are a wide variety of languages in the Forgotten Realms, and plenty of books won't be available in languages the character speaks (remember, translating a book involves writing out the translation by hand). If you can only read Elven, then most of the knowledge you get from books will be on topics that an elf thought was worth writing about.
6) Literacy might be rare.
In real world history, most people in the medieval period D&D is based off of didn't know how to read & write. This not only substantially reduces the number of people out there writing books (why learn to do anything that pays less than being a scribe if you already know how to read & write?), it also substantially limits who writes books. If only nobles and priests have both the knowledge and the spare time to write books, you should expect the list of topics available to be fairly limited. Admittedly, literacy may not be as rare in D&D settings (PCs can always read & write common, for example, though PCs are by definition a special case), but it's almost certainly not the >90% we're used to in the modern day.
7) Does the character's backstory actually give them time to read that many books?
Part of being a wizard is doing a lot of reading & studying, yes, but it's specifically studying magic. Wizards don't have innate access to magic the way sorcerers do, or clerics, or warlocks, or just about any other class; wizards get magic by studying and practicing magic a lot. Becoming a level 1 wizard is a lot like getting a PhD in neurochemistry; being brilliant helps, but it still takes years of focused effort. Even being an elf doesn't give you enough time learn magic and read up to expert-level on sailing, wilderness survival, monster lair layout, and all the other million and one things it can be helpful to know when you're an adventurer.
8) What world-famous library were all these books in?
When books are hand-written, copies are hard to come by. Many books will only ever have one copy in existence. A library with copies of even a quarter of the material plane's extant books would be famous across the planes, and almost certainly wouldn't allow random elves to wander in and spend a century or two perusing the stacks.
TLDR: Knowing lore, especially about old stuff, is pretty reasonable (though an appropriate knowledge check should still be required). Knowing how to do things should generally be a hard sell; few people have both the practical knowledge necessary to produce a book about mundane skills and the spare time & literacy needed to actually write a book (or hire a scribe to take dictation, I suppose).
Non-Canon Alternatives
The books don't really explain what elves actually do with all that extra time that doesn't involve being trained in every skill ever as well as being an accomplished mage, archer, and poet. Here are some options that rest on unofficial attempts to explain why elves are mechanically at about the same competency level as humans despite having been an adult for decades or even centuries longer.
The elf may not really remember everything he read while in long-time.
There's an excellent thread on the GitP forums, So You Want to Play an Elf, which, while written for 3.5, is largely fluff-focused and thus fairly easily translated to 5th edition. To summarize the relevant bit, it argues that elves perceive time differently than other races do: what shorter-lived races consider normal is short-time to an elf, and they only perceive the world that way in stressful situations that require them to do something out of the ordinary. Elves (unless crazy or very unlucky) pass the vast majority of their lives in long-time, which is a lot like being on a very relaxing sort of autopilot.
If you go with this interpretation of elves, then the elf probably has trouble consciously remembering things he read in long-time. Alternately he may be one of those lunatics who avoids or is incapable of entering long-time, but that would almost certainly give him a pretty poor reputation in elven society (which might very well limit his access to an endless supply of books).
Elves may focus on learning largely useless meta-knowledge, rather than picking up a broader knowledge base.
Another possible explanation for why elves aren't masters of every possible skill or talent is that when an elf learns something, they obsessively learn everything about it, spending a lot of time picking up trivia that few shorter-lived races would bother with.
A human trained in Arcana could probably tell you that the evil wizard is casting Hold Person. An elf trained in Arcana spent an extra thirty years picking up the knowledge needed to tell you that not only is the evil wizard casting Hold Person, the specific version of the hand gestures he's using is typical of the Broken Mirror school, founded by the tiefling Uk-shae 2217 years ago. The elf could further explain the history of that particular school/style of arcane magic, as well as each of the seventeen known variants of Hold Person's somatic component and their origins, plus which variant is a quarter of a second faster, which variant is a full 6% more mana-efficient during the current phase of the moon, and then follow up with a discussion about the philosophies of the various scholars (probably elves) who did the research to determine said speed and mana-efficiency.
With this fluff/crunch interpretation, elves definitely know tons more than shorter-lived races, it's just that most of that knowledge is completely useless minutiae. Elven bards could be the exception to this rule, or they might simply know a truly horrifying amount of trivia to match the breadth of their knowledge/skills.
Best Answer
Have an out-of-game discussion with your players about expectations.
This is a common issue with TTRPGs, especially with newer groups: When people bring their own preconceptions and expectations, they often end up trying to play different games, which causes a clash of playstyles and a frustrated table dynamic. And when one player's style is radically different from the others, they may end up becoming a problem player, even if they intend no harm.
It seems like your player has narrow preconceptions of D&D based entirely on a very specific DM and a very specific playstyle, and not from their own experience. In reality, there are many fun ways to run a D&D game, and very few of them involve mimicking Mercer et al.
You need to establish expectations with your players. Explain to your players that you are not Matt Mercer, nor are you any of their previous DMs (if any). You have your own way of running a game, and that's fine, you just need to communicate your style to them.
When having this out-of-game discussion, here are some example questions for you and your players:
For more questions, you may want to check out the same page tool for establishing expectations. The tool itself is a bit simplistic, but it may give you some inspiration of what topics you want to discuss.
One common method for discussing expectations is to organize a Session zero. Typically this conversation occurs before the campaign, but your current issues at the table suggest you should have this discussion ASAP.
That being said, it's still encouraged to make some accommodations for your players. If the bard wants an opportunity to discuss backstories, that's fine, just give them an indication of when. For example, maybe throw in some slow-paced scenes (such as during short or long rests) when the player characters can have these sort of personal story dialogues.