"out there" is farther and/or more indeterminate (uncertain) than "over there" (over there is ostensive, i.e. pointing in a particular direction)
"Everybody out there [in TV-land"] comprises a dispersed mass of people that the announcer cannot see—he has no idea how many they are, nor how widely they are dispersed; so they are not just "over there", they are everywhere (all around), near and far, but out of sight to the announcer. In other words, out there.
As to whether this applies only to TV announcers—no, a similar reasoning applies to, for instance, the search for intelligence in the rest of the universe:
"Is there anybody out there?.
Or to a more down-to -earth situation such as a mom standing at her back door, after dark, and yelling:
"Hey, kids, are you out there?"
She thinks they might be "out" in the back yard, and located at an indefinite "somewhere" but she cannot see them.
Expressions like your example..
"The Mongols being the Mongols..."
.. basically mean that what you are about to say is typical of the named person or group. Perhaps this is because you have already established this fact about them, or the writer assumes you know because it is widely known or believed.
For example, lets say you were writing about someone named Mary who was known to be quite contrary (that is, inclined to disagree or to do the opposite of what is expected). You might say:
Mary was ordered to go straight home. Of course Mary, being Mary, decided to go for a walk instead.
It is assumed then that the reader knows Mary to be contrary and so going for a walk instead of going home as she was ordered needs no further explanation because it is known to be in her nature to do the opposite of what is asked. If this fact about Mary was not known, you would have to introduce it, and you would instead write:
Mary was ordered to go straight home. Of course Mary, being contrary, decided to go for a walk instead.
I'm no expert on history and know almost nothing about the Mongols, but the history video you link to is speaking about civilisations, and how the definition of the word implies there is some settlement, or permanent land. The Mongols were known to be nomadic and barbarians, meaning they roamed around conquering other civilisations, so quite the opposite of settled or civilised. But they did settle in Yuan China and so are regarded as a civilisation and an exception to the "rule" that would classify them as nomads, I guess. Maybe the video creator is alleging that either the Mongols were known to be contrary, or possibly just the fact that "barbarians" (a term he uses) by nature are rebellious, and therefore prone to the unexpected?
Best Answer
See http://www.thefreedictionary.com/hold, definition 8: "Hold" can mean to assert, affirm, or regard in a certain way. That is, if you say, "I hold Bob to be an honest man", that means that you believe he is honest or you consider him to be honest.
If something is "widely held", that means that many people affirm or believe it.
So to say that this person is "widely held to be a great basketball player" would mean that many people consider him to be a great basketball player.
Lebron James is a well-known basketball player. So "widely held to be the next LeBron James" means "many people believe that he will become as great a basketball player as LeBron James".
(Or maybe in context they're talking about some other aspect of LeBron James. I'm not a sports fan and I don't know anything about the man, so if he's also famous for his charitable work or singing ability or whatever, it's possible that that's what they're talking about. But from the fact that the paragraph is talking about basketball, I'd guess not.)