I'm firmly convinced that the Iraq invasion was a NeoCon wetdream to restructure the Mideast, via the domino theory, into a peaceful region compliant to our (and Israel's) geopolitical interests.
The whole WMD threat was nothing more than a "bureaucratic" justification that they thought would work in the wake of 9/11, and Wolfowitz
said as much.
Saddam was a convenient boogeyman and the WMD/terrorism rationale was a threatening enough reason to justify their big adventure in the sandbox.
The Downing Street memo cast further light upon this (as did the Valerie Plame/Joe Wilson brouhaha). The NeoCon's had a compliant nincompoop in the White House (with a grudge), an strong ally there as well (Cheney), and a cabal of NeoCons in DoD (Rumsfeld, Wolfowitz, Douglas Feith) and a weak, easy to roll National Security Advisor, Condoleeza Rice.
Sincerely, I have no doubt about this being the case. However, America is unwilling to admit to itself that we spent so much in blood and treasure on such a cynical misadventure.