Barbara Hambly wrote that book a while back: The March Of Folly.
You are assuming their stated objectives are their real objectives. Their real objective (as for ALL politicians) was to make money and increase their power. The defense and oil companies have made money. That was the purpose of the war. That stuff about WMD and 'remaking the Middle East' was said to fool the peasants. If you don't want to be fooled like a peasant, then learn to think rationally about those who have power over you.
Let's trade charges of irrationality. It's one thing to believe that the administration just wanted to line the pockets of its cronies, but quite another to think they've succeeded. Without a stable Iraq, billions of dollars of reconstruction will never happen, and hundreds of thousands of barrels of oil will never be pumped.
Even if the "real objective" of the administration was self-aggrandizement, a stable, Saddam-less Iraq was in their interest. This was precisely my point: it didn't much matter what their "real objectives" were, because they aligned with good outcomes for most Iraqis. That we aren't seeing those outcomes isn't evidence of a secret plan visible only to the rational, it's evidence of failure.