If 9/11 wasn't blowback, why didn't this SAME group of Islamists attack us when we worked along side them to combat communism? We got along perfectly fine then. It wasn't until several years later, after more wars in the middle east that the anti-american sentiment in some places built up. Thats when 9/11 happened.
And if they are motivated by nothing else, why did they target the United States when they have like 60 countries which are closer and more accessable for attacks?