Bluesky momentum
There may be several reasons why Bluesky has gained a lot of attraction at this moment. In my opinion one of them is that the social network is able to imitate X (Twitter).
Unlike the Fediverse, there is only "one instance" on Bluesky, simple features like quoting a post have been implemented for a long time, while for example Mastodon will introduce it in the next release.
It is very easy for people to switch from X to Bluesky.
That's it.