I am currently playing a Tabaxi Druid, Circle of the Moon. I wanted to flesh out his backstory, so I read up on them in Volo's Guide to Monsters. In a box on page 113, it said:
In the Forgotten Realms, tabaxi hail from Maztica, a realm
located far across the ocean west of the Sword Coast. The
tabaxi of Maztica are known for their isolation, and until
recently they never ventured from their homeland. The
tabaxi say little of why that has changed, though rumors
persist of strange happenings in that distant land.
I thought that it would be interesting to have my Tabaxi immigrate from Maztica to Faerun, and then travel to Chult for the current adventure, Tomb of Annihilation. There's only one problem: I don't know why my Tabaxi, along with many others, left Maztica. Are the problems detailed in a published adventure, or does Volo's Guide just leave it up to the player? I want to roleplay my character better, and I think that knowing what happened to my home island will help.
Best Answer
Disclaimer: The following is speculation based on information about other areas that suffered a similar fate.
There is precious little information available about Maztica, especially in this regard. However there is some informed speculating we can do to help you come up with your own story.
During the Spellplague, Maztica was switched with Laerakond (although not in geographically identical spaces). Maztica was sent to Abeir, while Laerakond came from there. (Abeir was a second planet that was once merged with Toril). Maztica returned with the Sundering, and Laerakond also remained.
The kingdom of Unther (a human empire) also switched with Tymanther (part of a Dragonborn empire), which brought Dragonborn to Toril. Unther returned (most of Tymanther switched but some remained) with the Sundering. Unther has been mostly destroyed and overrun by the creatures in Abeir (mostly Genasi I think), and had only recently regained their kingdom before returning to Toril.
Using Unther as an example, we can maybe speculate that Mazticas stay in Abeir led to strange changes in ecology and the political landscape. Especially if Maztica was connected to a new landmass, it could have been ravaged by new diseases, strange beasts, or empires looking for easy conquest. Theres already some record of diseases running wild there after colonists from Faerun attempted to establish cities.
TL;DR Maztica was sent to Abeir, and likely had any number of strange developments on that new planet. Now that it's back, perhaps the Tabaxi are fleeing some lurking danger that they could not escape until now.