And they usually solve problems through violence. Meet the new leader, same as the old leader, happy to continue running things to the ground for the ordinary human on earth. We can hope that recent elections have started to cause people to look inward for the source of the world's problems before it's too late, because if they keep looking at the other then things are bleak.
Any movie where someone comes in and hates everything you're about for no reason and leads the protagonists blameless is just action filler and, though entertaining to the common folk, does nothing to explain why there might be sincere reasons for discontent among the many peoples of earth.
Any politician that doesn't ask the people to assume some responsibility of their own in fulfilling the duty of a citizen to stay informed and involved and be mindful of their impact on the earth is just as empty, but in this environment that kind of talk would be political suicide.