While MLK changed America, I would argue that in changing America, he changed the world.
MLK was a great man for sure and he pointed to the way to achieve his goals.
However, MLK had the world behind him (except SA of course), he had the legal system behind him, he had the political system behind him and he had a LOT of resources .... very smart group of blacks and whites.
Mandela had none of that. on the contrary all those who were behind MLK were in one way or another against Mandela, or at best on the fence. Afraid to offend the so-called civilized nations.
Ghandi were also a great leader but he was not fighting HIS OWN system of apartheid. He was fighting a foreign occupier. that is a BIG difference. with all of 500+ million people behind you, your chances of prevailing is not small at all.
Mandela???? who was behind him? about 10+ million of uneducated, homeless and unorganized people who were deprived of all kinds of rights and sustenance? It is no less than a miracle.
As for Churchill .... pleeeeease dont get me started.