I usually agree with everything you write. But I'm going to say it:
Twitter isn't a public space.
Comparing two cities which are both public spaces, to one public space (mastodon) and one private space (twitter) is difficult.
Why people choose the private party is a serious point worth acting on. No problem with that argument.
The research suggests people left twitter too quickly anyway. A more protracted campaign of inviting folks over would have worked better.