With current synchronisation problem between instances, choosing a big instance is a no brainer. I don't want to use small instance and got 404 when searching community on other instance or when not all comments from other instances showed up.

I use Gboard because the prediction is better than the others. As a Japanese speaker, the choice is limited.

Asteroid problem is more solvable than political problem.
Armageddon solved it like in 2 hours or so.

not enough of those famous and important people moved from Twitter to Mastodon

This is the reason I'm still using Twitter. I use Twitter not to tweet about what I did, but to get news from people I follow.
Tech people can move to Mastodon because their circles are moving, but not with common people.
For me, personally, Mastodon is like empty void. No one to follow and I can't interact with people who share same interests because they only exist on Twitter (since the "famous people" isn't moving from Twitter)