No, not the only one, but if one were to ask them why they picked the targets they did, they'd describe it religious terms (talking about infidels, jihad and the great Satan) not in Marxist terms (i.e., economic oppression).

Just as an aside, "economic oppression" isn't a uniquely Marxist term, nor am I even aware of a specific Marxist definition of it. Are you thinking of "economic exploitation", perhaps? The latter means the difference between the amount of wealth generated by labour and the amount that labourer is paid.

I am pretty darn thoroughly convinced (though of course I am open to changing my mind) that the idea "religion made them do it!" is overly simplistic. I used to hold the position you do, but over the course of several years of examining the issue, I have come to the conclusion that the use of religious terminology and phrasing and all the general trappings of Islam are, while perhaps truly believed, are for the most part merely a rhetorical device constructed to take maximum advantage of the society they are recruiting, living, and (typically) acting in. I'm hesitant to say this next sentence, politics being the mind killer and all that, but I shall anyways (I have noticed I am in a hole. Hypothesis: if I dig long enough I'll get to China!). Osama bin Laden talks about "defeating the Great Satan for the glory of Allah and Mohammed (pbuh)" for the same reason George Walker Bush talked about "spreading Freedom and Democracy": because it resonates with his intended audience, convinces them that he has similar thought-processes to them and is representative of their interests, or at the very least their team, not because he (edit: necessarily) believed that that was what he was doing.

In fact judging by the fact that most of the hijackers were from wealthy families, I'd guess they didn't really care about the economic dimension except as part of a general attitude that our decadence is sinful and is spreading to the middle east.

Most people who have had impact in the world have come from wealthy (or at least not working-class-poor) families, including probably every Socialist Revolutionary you've heard of (Marx, Engels, Lenin, Che, et cetera), not to mention almost every politico in general. If anything, being middle class (inasmuch as that term makes sense) makes you more likely to simultaneously see the degradation of the poor and have the education to see what (at least seem to you) like plausible explanations for it. And then if you're an engineer or what have you, you have access to abilities that can actually do something about this (build bombs, fly planes, whatever), or the funds to support yourself while you learn them, or whatever. The point is, being middle class is not likely to make you less politically aware and active than being poor, and it is likely to increase your free time and ability to do things politically, including but not limited to committing acts of terrorism.

I stand by my advice as good advice. If you want to successfully model others' behavior, you shouldn't assume they see the world the same way you do.

When phrased this way it seems much more like actual advice and much less like an insult. I'm not sure how much of this is my inference and how much is your implications, but it's kind of moot. No hard feelings are taken, hopefully none were intended. Friends? I certainly agree that I should not model their minds as being identical to mine, but given that I don't want to kill people, I'm already doing that at least to some degree.

That said, I think that you are being overly simplistic in your model of these people. Again I link to this page. Could you please explain, or link me to someone else who has, what makes you think that your model of their minds and motivations is more accurate than mine?