This happened on Mastodon multiple times as well. Something happens on twitter and theres a huge exodus but they never stay
I believe the biggest reason for that is because the people exodusing there aren't that interesting and without algorithms and pre-elon Twitter's moderation they just dont get any attention or social authority. For example George Takei - he landed on some random mastodon server run by some dude. What a nightmare. Takei is on bluesky now lol