I know I hold a seriously controversial view here on r/atheism, but I think that the hijackers' reason for attacking the US had more to do with politics and America's current occupation of the middle East. Even in 2000 they had bases in almost every country, and were well-known as an evil tyrant nation bent on destroying freedoms to extract resources. This is how almost everyone in the Middle East views the US: as an existential threat.

What you'll notice about Osama's addresses is that he didn't go on about how un-devout you all are as much as how evil your country supposedly is. Remember also that suicide bombing was invented by a secular movement called the Tamil Tigers.

Im not saying religeon is good, in fact I think it as much a tarball of archaic coprolite as you all do, but I think it doesn't pay to see it as a source of all this stuff 100%. I agree it has only negative influence, because of the way it allows people to live and be comfortable with completely irrational worldviews, but as a dialectical materialist, I consider economic and geopolitical circumstance to be the cause and determinant of ideology, not the other way round.

Edit: forgot Osama is past-tense