Again, I have no first-hand knowledge. I have heard numerous speculations:
1) Washington wants to control the price of world oil (both to give DC better ability to modulate the US economy, and as a threat to other oil-producing nations to cooperate with us or face a price collapse).
2) Iraq switched its oil accounts from dollars to euros a year or so ago. This was a blow to the status of the dollar as the world reserve currency which, if emulated by other OPEC nations, would have severe negative economic consequences for the US economy.
3) It was an attempt at radical Reconstruction of the Middle East, similar to the South after the Civil War. One theory states that terrorism is endemic to the Middle East, and the only ultimate way to end it is to essentially invade and conquer the entire region, and then give them mass doses of US pop culture to transform them into clones of American consumerist sheep.
4) It was an attempt to show the Arab world just what we are capable of. The US couldn't allow the 9/11 attacks to go unanswered...we had to kick Arab butt...and Saddam was the most convenient target around.
5) And last, but not least, there is the ever-present theory that the Likudniks in American precipitated the war to shape a more secure environment in the Middle East for Israel.
Take your pick. But as I said, the only thing that I am fairly certain of is that the stated reasons (WMD and links to Osama) were BS.
I think #3 and #4 may be plausible in some sense.
More likely we must face the probability that, as Wolfowitz told Vanity Fair, there were multiple reasons.
The euro move did indeed hurt, but I can't imagine even Wolfowitz plumping for a wat just to remedy that. I think the oil market pluses were just fringe bennies, to be honest.
For now, we must face the reality that we still do not know what happened to Saddam's stockpiles - stocks we know existed in some significant form at one time. I find it difficult to believe that all he had were a few half empty drums and empty mobile bio lab trucks lying around, because he ended up paying a very high price to hide something that did not exist.
It will be embarrassing for the administration and Blair if we end up unable to produce such explanations for the WMD's. But there is also no question but that the removal of Saddam from power was a good thing.
Depressing though the prospect might be, I would far rather the Arabs end up becoming consumerist sheep than sitting unemployed around the madrassas all day hatching plans for killing us in mass quantities.
In the old days we would have done far worse.