>>40557854 (OP)Watched this recently but I don't remember the ending. Must have passed out drunk.
Anyway, yea they're here and they've been here. They didn't expect their livestock to grow so large in numbers, but decided to let it go as they had become obsessed with human nature (this is where reality TV came from).
They revealed themselves after the world wars, when it was clear that their creations could finally impact their subterranean homes. They compromise people by replacing them with skinwalkers and steer the world to a great culling of the herd.
Tl;Dr we are their food and we got out of control.