Since you asked, G.W. Bush & Dick Cheney were bloodthirsty for a war. They and all their cronies had their hands in the till for war profits. That's just two reasons, but I'm sure there are more.
Anyone who still thinks a plane crashed into the Pentagon is either uninformed, blind, ignorant, a Sheeple, or in major denial.
I don't think it is that simple. Your government would not need to take such drastic measures, after all it is enough for example to lie about weapons of mass destruction or do it in some other less riskier way. Thinking that your government did it is just ridiculous and far fetched.