Two points, firstly, people often act irrationally and believe it makes sense at the time. Secondly, I wouldn't suggest most decisions are made on a single impulse but a complex interaction of a mix of motivators. What I mean is, to one degree or another some or many of the leaders of some of the crusades were motivated by reports and/or desires of great wealth...but that wouldn't be in a vacuum, they were also concerned about reports of pilgrims being killed on the way to the holy land, and some perhaps as a retribution of incursions of muslims in previous centuries...and some for those reasons and the chance of glory in battle. We don't have the same worldview that was common to those times, so the reasons that motivated the crusades wouldn't necessarily make full sense to us in our day.
I would more or less look at it like that. The catalytic motivation was, I believe, genuine.