Bluesky users don't really care about federation tbh. For them, it's the new twitter.

Then there's network effect. Unlike Fediverse that attracts tech-savvy people for the most part, Bluesky has a very diverse userbase - and that userbase expands rapidly because of the aforementioned network effect.

I bet most of new bsky users are probably not even aware of Fedi alternatives like Mastodon.

Depends how you want to engage with the world. If you want to follow topics, the fediverse is great. If you want to follow people, you go where those people are, which still might be fediverse, but maybe not.