Hegels philosophy was a heavy influence on a lot of different groups. Marx, Engels and Feuerbach used a lot of his work, especially his thoughts on history, who where also shared by the Fascist movement. Isaiah Berlin called him one of the architects of modern Authoritarianism, and in fact, I can't think of a single authoritarian or totalitarian state since the 19th century, that wasn't in some way inspired by Hegel.
Of course, how big that influence finally was, is up to debate, and there are a lot of angry german philosophy minors who will tell you, that he was just some kind of spiritual grandpa to Marx. But the high ranking mirrors my personal interpretation of him and especially german history and I'm quit comfortable with it.
Secondly, Christianity grow relativly graduatly at first. The historic Jesus only directly affected a small community, and when christianity grew into a wider phenomenon, it was already filtered through other people like St. Paul or St. Frumentius. Muhammad and Confucius had more hand-on political influence connected with their ideology, with Mohammad leading the Rashidun Caliphate and Confucius being a political advisor.
(Although I plan on updating the Quiz anytime soon and the top spots will certainly be reevaluated.)