I'm of the opinion that is God who places people and civilizations in positions of leadership and power. God chooses kings and rulers, for his purpose.
Lets use a much more down to earth examples than Winston Churchill, Eisenhower, Stalin, Hitler and the rest of that eras greatness and great evil, for they all played a roll, served a purpose, most of which I can not understand for God alone knows.
Yet, think, "The Beatles." 4 such talented, handsome,witty, sharp, intelligent, rebellious, tough, strong, determined dedicated individuals have not existed before or since in the world of Pop music, yet, those same 4, at any other time in history, would have amounted to little or nothing. Timing, is everything.