Usually, that's because a different director takes over but this was Rob Zombie who directed the first 2. That said, one of the leads Sid Haig, a b horror movie legend died during filming, which probably caused a script rewrite which was not good.oh the evil within has the guy from "The Hills have Eyes" my mistake
there's a lot of bad movies out there especially horror sequels, seems like trading off the success of one is part of the industry