“ Why did all the Democrats vote for this?”
Why wouldn’t they?
What point are you making? What is your reasoning.
If your question is not rhetorical the answer is that McCarthy is not in their party and it gives them a chance (remote to non-existent) to elect a speaker from their party.
Because logically the argument being presented here does not make sense.
If McCarty is the best Speaker the Dems can hope for out of the GOP, why not keep him in place? Why would the Uniparty allow their tool to be fired?
I guess maybe the mistake here is to think logic has anything to do with politics.