@zuiderzeemeermin re: "why not just have them migrate here?", for the same reasons we couldn't get twitter users to migrate here. it's a mixture of cultural and technical limitations. from the woes of federation bugs, to the lack of discoverability (fwiw i adore the chronological following feed, but this is particularly devastating to most artists), to the simple chicken-and-egg problem of "my friends aren't here already, so i won't bother".
bluesky was also particularly welcoming to the immigrating twitter crowd (the user interface is very familiar, engaging with the platform was almost identical to twitter, etc.). the fediverse (in my view) has instead been actively hostile to most twitter refugees. many cool instances i federate with have mastodon(dot)social (who we understand to be the "flagship" instance) blocked or limited in some way. the environment, for those on the outside, appears very cliquey, and that's really intimidating when you're potentially moving your entire online identity somewhere. that's not to mention the regular occurrence of "fedi meta/drama", which i've been told by outside sources has been a particularly sore spot.