© Charles Chandler
One of the defining characteristics of a cult leader is that he figures out that it is easier to manipulate people using a gimmick. A normal egomaniac wants to get people to do things for him, and the more obviously the whole thing is about him, the bigger he feels. This explicit selfishness limits the scope of his influence to that small number of people around him who have their own selfish motives for wanting to make him happy. But a cult leader knows that if he can convince people that it's not about him, but rather, that there is a greater good to be achieved, they will be willing to do things for him in the pursuit of the greater good. To the manipulative person capable of maintaining this layer of abstraction, this is a Really Good Thing.
The gimmick can be anything, but somehow, it needs to be capable of dictating behavior, or it wouldn't serve as a conduit for manipulation. Typically the gimmick is a religion, with a moral code tailored to suit the selfish desires of the leader.