I don't understand why anyone would ever get onto a new commercial social media platform again now the Fediverse exists.
Lots of reasons:
It's bigger and less fragmented. More content, more diversity, more activity, and it's all in one easy place.
No extra conceptual hurdles to overcome like "what is an instance" or "which instance do I join".
Network effect. See point 1. Unless you are some kind of FOSS enthusiast or a refugee of every other social media platform due to your vulgar, sexual, illegal, and/or politically extreme interests, your friends, followed creators, and other people of interest have a far higher chance of being on BlueSky than the Fediverse.
An actual algorithm. Many people who jump to the Fediverse hate it, but a silent majority of casual users actively want it. Meticulously curating your own feed is not a boon to them, it is a chore.
A lot of the crap that the Fediverse did not inherit from its commercial counterparts is precisely what a lot of users are there for. And a lot of the expanded tooling and control the Fediverse alternatives offer are pearls before swine with most of these folks. Overall it just makes the Fediverse appear flakey, underbaked, and devoid of content.