At least in my experience it wasn't all due to Musk. My part of the academic world was quite small, and seemed to be increasingly uncomfortable with the enshittification of Twitter before Musk's purchase. Observing that the new owner was a shitlord probably coordinated a departure earlier than otherwise would have happened, but I think the process was well underway already.

We mostly ended up on Mastodon, I think. Personally I'm quite grateful that it's no longer professionally necessary to have an extra social media account.