The main objective of the first crusade was to make the trip to Jerusalem safe for pilgrims
I dont think it was that simple, it seems more than anything the 1st crusade was simply a tool used by the papacy to increase its influence, territory and divert thousands of restless would-be knights from fighting each other and instead aim their war-lust at the islamic world.

Wernt some later crusades aimed at pagan *barbarians* though, surely conversion was the main idea of those particular crusades.