so I don't know if normal people will ever watch this movie. The cast being all mainstream actors is what surprises me

I would bet that many normal people will end up watching it specifically because of those big name mainstream actors. If it was just unknown actors, I would agree that no one except ultraCHUDs would ever see it. But I'd assume that's exactly why Benny boy et al threw a lot of money at these big name actors, to ensure it would end up being more broadly seen.