It's not poverty that does it -- it is envy and excessive self-esteem. It is the lust for status and other rewards, in excess of what the person is able to fairly earn.
These people, like Atta, Osama, and the rest -- they were not happy with being relative nobodies. Osama could have made a good living working as a manager at his father's construction company. His overgrown ego wanted more.
These terrorists are in it for glory and power, especially including power over any infidel women who come into their possession.