the only people I know who use Bluesky are basically moderate and self-styled “progressive” liberals (think “resistance” libs in the U.S. who vibe more with Elizabeth Warren’s elitism than Bernie Sanders’ populism)

I’m out of the loop on Bluesky’s current bonfire (feel free to educate me if you feel inclined, but I don’t want to put work on you that you don’t feel like doing), but wouldn’t Mastodon have already appealed to users who left Twitter for Bluesky in the first place? It seems like being an exclusive Bluesky user already has a selection bias for people who aren’t going to use Mastodon, since that’s where people migrated to first when Elon acquired Twitter.