By now I'm fairly convinced /by research data, but not claiming it's conclusive/, that both types of leaders - whether self-interested or self-sacrificing - are actually irrational. It's the element of irrationality which empowers them over other people, who wouldn't know what to do, in cases when nobody knows. Then, decisive irrational folk emerge from the chaos of personalities, in order to act, no matter what.
The main argument is that this was much more needed in a primitive highly unknown and insecure environment of crude wilderness, and is gradually becoming less needed; as well as leadership in general.
Along with leadership losing its importance and social status, irrationality loses its dogmatic relevance in the life of humanity too. /which gets us back on topic/