I think what's going on in those cases is that people are heavily invested in Twitter, believing their bulk audience is there, but (understandably) want to hedg

I think what's going on in those cases is that people are heavily invested in Twitter, believing their bulk audience is there, but (understandably) want to hedge their bets. Lots of them are posting the same stuff to both Twitter and Mastodon (tooling exists) and they'll wait and see how it pans out. As they see more interaction on Mastodon, perhaps they'll migrate their focus, too. Interesting time, for sure.