If you still believe that the Christian Crusades were driven exclusively by religious motives, I think you must not have studied them carefully, nor studied the subsequent history of conquest and colonialism by the West around the world.
Religion was certainly a factor, but hardly the overriding factor. The promise of financial gain and access to new markets was perhaps the most significant impetus for the Crusades; just as these were the key factors behind every military campaign of imperial expansion and colonialist occupation that followed; including the genocidal conquest of America.
Against the Muslims, it was justified as a war on “infidels”, against the Native Americans it was justified as a war on “red savages”, in Africa it was the “White Man’s Burden” to “civilize” the “heathens”. But, by and large, these were all commercial endeavors, for markets, territory, and resources; no more no less.
The Crusader armies were made up primarily of “second sons”, the landless offspring who had seen their fathers’ property bequeathed to the first born sons; they were poor, dispossessed, and were looking for land and riches. Just like the poor and dispossessed that set out for the “New World” looking for land and riches, to be seized from the Native Americans. They were, basically armies of land pirates. Their religion was plunder, and it still is.
Religion is just the main rationale, not the main reason, then and now.