Why did this put Threads first? It's not chronologically? And it's not user counts? This seems free advertising for a service that hardly compares even with the likes of Xhitter - which isn't even one of the options?

As the recent USA election shows, nothing is billionaire-"proof". They could e.g. put huge tariffs on purchasing server machines, or on non-mobile-device internet access, or use of any IP address that is not registered with a central authority and verified(TM) to run only M$-"approved" software.

Also I thought there is no (real) account migration on Mastodon either (at least, people have definitely reported feeling "stuck" in that while they can move, will any of their followers be able to successfully follow them after they do?). Nor can celebrities prevent people from impersonating them on new instances - which according to them is why they haven't joined it (last I heard).

Sorry, I am probably vastly overthinking this, and the graphical style is cute. I think I'm just overreacting to the idea that Mastodon seems to be having an identity crisis where it both wants to be something entirely different than Xhitter, while also competing with / replacing it at the same time, yet refusing to do the things that would make that happen (like make changes to be more welcoming to celebrities). If we want to remain a niche, like a federated service for the common person, then just do that?