The supposition that "the Saudis are not clever enough to do it" is a sort of racism, as much as "this is a typical Jewish trick." The upper crust of the Saudi royals and govt and industrial functionaries have been sent to the very best (and most expensive) American and European universities and business and technical academies. And Saudi oil money has been able to attract some of the brainiest non-Arabs from around the globe.
We have here at least 3 situations, probably more: (1) There was considerable evidence in the original investigation pointing to Saudi complicity of some sort in the Sept 11th attacks (we still don't know the details) - which Cheney/Bush very deliberately lied to all of us about, and instead misdirected us to Iraq, leading to (2) a pointless, expensive, wasteful, bloody and ruinous war in Iraq, for which we will be paying and regretting for decades to come, and (3) in the meantime, without the help of the original investigation report, the litigators in the Sept 11th lawsuits were able to establish Saudi liability - a pretty big achievement in legal annals - and the Saudis are attempting to extort their way out by threatening to destroy the US economy (to do this may eventually cost the Saudis more than just paying the court judgment, which suggests that the Saudis might be trying to hide a lot more liabilities). The Saudis were supposedly our good buddies among the Arabs; they allowed us to maintain an airbase in the broiling desert, just so long as we paid them an outrageous rent for the sand and didn't send any Jewish servicemen or any USO, and they required the USAF to provide them with eavesdropping on Israeli military radio transmissions; and when we asked them to help interrogate suspected Al-Qaeda affiliates they sent us only garbled, truncated transcripts that were mostly unhelpful. When you've got friends like the Saudis, you don't need enemies.
"Rebellion is as the sin of witchcraft."
First Samuel 15:23