And even then glass onion barely feels like it stands in the list you’re trying to make because there’s plenty of crime and detective dramas that don’t focus on the super wealthy.

This is incorrect. It’s a convention of the genre that an heiress/tycoon gets murdered and the detective tries to solve it, typically in a mansion.

This goes back to Agatha Christie, unlike OP was saying, but it seems pointless to deny the class bias exists. Obviously the class bias exists.