It is not required that someone be a person of character in order for them to be a leader. Very professional example of leadership. Maybe not to you, but it may matter to your victims. Leadership without character is hell. Powerful humans, unrestrained by conscience, create a hell on earth for other humans, for animals, for the ecological balance of the earth.
History is written by the victors, and the victorious are by definition effective leaders.
They may also be depraved. No doubt leaders of the Holocaust thought they were serving a great cause. They were willing to die for their cause, and many of them did. Humans have a fearsome ability to rationalize. They think they are the cause.