Hi Rasputin
Good review.
The Wikipedia article over-generalizes.
During the first crusade, at least, most of the nobility were landless second and third sons who were seeking their own place in the sun (no kings went on the first crusade). The church's big reason behind promoting the first crusade was to get the large number of unemployed soldiers out of Western Europe. A recent spate of pilgrims (tourists) being robbed or taken hostage en route to the middle east pilgrimage sites (tourist destinations) was another reason.
So, the image of a mob of religious fanatics setting off for Jesus is an over-simplification.
The thinking of the first crusading army as a mob is not off the mark. The Crusaders of 1099 experienced a series of extraordinary lucky breaks (against the Turks in Asia Minor and against the Egyptians at Damascus and later at Jerusalem). This fantastic luck contributed to them believing that they had god on their side.
Source: Sir Stephen Runciman's "The History of the Crusades" Vol I.
I know far less about the later Crusades. By the third crusade, when Richard the Lionheart and St Louis (the first wave of royal crusaders) entered the fray, the middle east was a mesh of petty kingdoms, some Muslem and some Christian, shifting alliances between each other. The interlopers from Europe (ie. Louis and Richard) were there for glory, didn't understand the subtlety of the political situation, and skirmished with the Christians' Muslem allies. Saladin and his predecessor, Nur ad Din, wielding awesome military might and forcing alliances from the Christian-friendly muslems annihilated the Christian forces in battle after battle.*
* My knowledge of the third crusade is hazier than the first, because I never finished Runciman's "The History of the Crusades" vol 2. The subsequent crusades were sloppy campaigns to regain what was lost in the middle east. One crusading army even sacked Constantinople. Another was butchered to the last man in Asia Minor.
A major ally to the Western Europeans were the Genoese, who profited much from holding monopoly over the sea trade routes from the Levant, and also made money transporting soldiers and migrants to and from the Levant.
The crusades make really good reading.
-Tim