In answer to the four myths:

1. Pretty much on the money, though things would have been better had the Crusaders simply listened to the Byzantines, instead of going off on their own.

2. Some went for the plunder.

3. Some were quite cynical, others quite sincere.

4. The Muslims already knew how to do those things--though having gotten their butts handed to them several times by the Byzantines, they were often willing to observe extended truces and even have normal relations with them--for which the hairy-chested Franks considered the Byzantines a bunch of pansies and suck-ups. Ironically, within half a century, the rulers of the Crusader Kingdomes of Outremer were behaving in exactly the same way, and for exactly the same reasons.

Not mentioned here is the qualitative difference between the first three Crusades and the last four. The latter crusades were mainly cynical free-booting expeditions that did no good for anybody--not the Crusader States, not the Byzantine Empire, not the indigenous Christians of the Middle East, and not the Arabs. The only people who benefited, in the long run, were the Turks.