I'm sorry, but this video rotates 90 degrees.
As for not being a definitive set-up, Chomsky either hasn't read, "Day of Deceit: The Truth About FDR and Pearl Harbor," by Robert Stinnett or he's blown it off.
Also, the Vulcans took the path of least resistance and wanted a wider war for Afghanistan's gas pipeline plan and heroin, to hit Pakistan, to surround Iran, to butt up against India and China, etc.
Al Qaeda was and is supposedly borderless/amorphous, had been the more recent bogeymen what with the USS Cole attack pinned on them, and it was easier to get Saudis in and out of the country than Iraqis.
There are many other reasons too.