There's two ways to be better than other people; to rise above them, or to drag them down. Bullies want to feel important just like everyone else, but they are not confident in their own abilities, so they are afraid to try growing themselves, because they fear they will prove to themselves they are as stupid as they fear they are. (the ol', too afraid of failure to succeed) They are naturally left with either accepting they are a failure, or throwing other people under the bus.