Columbus is an interesting case in the 'great man' debate. Had he not talked people into backing his voyage, would someone else have done so? Mark Kurlansky makes the argument that when British and French explorers were beginning to explore North America, the islands of the northeast of what is now Canada, they found Basque fishermen. But was that before or after Columbus that the Basque began fishing the region? And would word have gotten out? The Basque, apparently, weren't talking.
Of course, we know today that the Vikings discovered America some 500 years before Columbus. But the big difference between what the Vikings did, and what the Basque may have done, and what Columbus did, was that Columbus told everyone about it. So it became common knowledge because of Columbus, where it had not based on all of the other people who knew that the continents of the Americas existed.
So Columbus, even though he was personally a monster, and his efforts triggered one of the greatest tragedies of human history, can be argued as a person who's individual efforts and leadership made a major change on the history of the world.
