What happens, in short, when Bitcoin ventures outside of its tight community of enthusiastic anarcho-libertarians
It has already done that long ago. Do you think Wall Street wasn't involved in bitcoin trading in 2019?

You make good points. Maybe all of the downsides of the ETF I listed here have been priced in already.
I would think that the ETF moves the "serious investor" scrutiny way, way up, but... maybe I'm wrong about that? We'll see.