yes, its a chicken and egg problem and a huge hurdle for literally anyone trying to create new platforms.
its about feature parity (even if they dont really exist, re:account portability), marketing among other things. bluesky is run buy a bunch of big names who were able to draw an initial load of users which got their ball rolling.
brazil jumped from twitter, that was a huge part of it. the election caused another wave.
bluesky is just twitter with faux-federation. it will end up with the same issues eventually when its board decides to recoup.