How many Crusades were there 12 I think I can't remember. It was a fight for land. The land worshipped by all sides. Muslims, Jews, Christians. You have to look at the time Christian Pilgrimages were attack in Europe also due to the lack of belief. The Muslims were not the first to attack Christian Pilgrims.
Though I don't agree with Muslim doctrine you and I have discussed this before. Each crusade was for control of land.
But why ? Maybe because the land (we're talking continents, folks) was STOLEN by marauding Muslims, who not only stole the land (continents), but forced the inhabitants to submit to the Muslim ideology (masquerading as a religion). And what a surprise...when the Arabic meaning of the word "Islam" is SUBMISSION.