Psychopathy can sometimes be a positive asset in politics. This dramatically slows down how quickly we can move anything forward on the larger scales. You just can’t make everyone have the same values, that would destroy the very innovativeness and adaptability that we prize so much.
For instance, had the Israeli PM working on the peace deal never been assassinated and replaced by Netanyahu, our world might look very different today. That one bullet, fired by a psychopath, killed someone who did study history and replaced them with someone who did not.