Coyle 1. I’ve encountered a few explanations to account for this “baffling success”: 
a) the Muslin defenders of Jerusalem and Palestone didn’t see the First Crusade coming, and didn’t take it seriously at first—the “Franks” were thought to be barely capable of wiping their own noses, much less doing war effectively;
b) Palestine was continually contested territory, and any military activity there, whether Fatimid, Abbasid, Turk, or Byzantine, was an “foreign war,” with all of the attendant logistical difficulties—if the Crusaders had invaded Cairo itself, the outcome probably would’ve been very different;
c) the Crusaders’ way of doing war was different enough that the defenders could not effectively counter it—heavy cavalry trumps, and the defenders didn’t have any (or enough, at least);
d) Deus vult.
2. That perspective IS kind of embedded in Urban II’s speech, in which he rails against the feudal aristocracy for disrupting society with their own military squabbles—from one angle, that speech could be read along the lines of “Hey, you kids stop playing army in the house! Go outside to do that!” Pillaging was part of the Crusades, but it was a part of all medieval warfare, regardless of the target. For most of the last century, it tended to be said that the Crusades were really motivated by economics and a desire for territorial acquisition. That view’s been contested in more recent decades, though. Most Crusaders actually took a financial loss to go Crusading, and that was part of what made Crusading a penitential act. Yes, Europe was enriched culturally by its encounter with the Islamic East, but I’m pretty sure the Crusades didn’t turn a profit in the more usual sense.
3. You left out the Campus Crusade for Christ! Certainly the anti-heretical Crusade in France and the anti-pagan Crusade in the Baltic (Nathan’s Teutonic knights!) are worth discussing. Still, it made sense to me that we left them out of the conversation: the conditions of those Crusades were radically different, and they form no significant part of the Crusades in the popular imagination, so far as I can tell. (The one exception I can think of is the role Catharism plays in the vein of conspiracy theories that underlies The Da Vinci Code: the Cathars are, reputedly, the link between the Gnostic and the feudal culture that gave rise to the Arthurian Grail legend. It is difficult to cast the Cathars as the keepers of the “married Jesus” secret, though, since they believed sex and reproduction are evil. That’s just one of the things Brown et al. get 180 degrees wrong.)