That's always the problem with this type of question. There's no single answer, just an overlapping confluence of bad choices, poor saps and real crooks. Let me offer my own incomplete breakdown:

• Fight terrorism: Joe American Average
• Cheap oil: Dick Cheney and pals
• Bring democracy to the middle east : GW Bush, Paul Wolfowitz
• Thwart China : Dick Cheney, Don Rumsfeld
• Eliminate WMD : Judith Miller
• Eliminate Saddam : Joe American Average, GW Bush ('cause he tried to hurt my Poppy)
• Divine intervention: GW Bush (God told me to...
• Line my pockets: Richard Perle (lightweight), Dick Cheney and pals (heavyweight)
• Election stategery: Karl Rove, all those !@!*#&^ Democratic reps and senators who voted for this crap
• Ego trip : GW Bush, Don Rumsfeld

Regarding the "ego trip" category, I remember reading somewhere that Bush was musing about being a "Wartime President" before he was even elected, "because all great Presidents had been Wartime Presidents". Is it real or or a figment of my delirious and hatred-filled imagination? If anybody has a pointer to that... I believe it was one of his campaign advisers or big time donor/family friends who reported that but I can't find it on the Internets.