I think a good amount of it is also "the straw that broke the camel's back." Twitter users have been taking abuse after abuse. Like many others have stated, they use Twitter to follow specific people. If those people aren't on other platforms, then they're going to stay. But after a certain point, the cost becomes too high. Now the platform is rebranded and now it looks as alien as it's begun to feel. I think that's why so many are once again leaving. Before they could just ignore everything else going on and try to move on with their day. Not there's a big, fat X reminding them of how much they're starting to/already hate the platform now.