They know, well, that people don't want auto-play video with sound.
History has shown that users will block such things with a vengeance or walk away from a service that won't stop this sort of nasty behavior.
Yet FACEBOOK is going to try it again. Like it wasn't fucking obnoxious and undesirably the first umpty-fuckin-bajillion times it was tried.
But hey. Go ahead! Make your platform ever more irrelevant! All in the name of chasing ad dollars!
You fucking twits...