The "why" of something is never due to anyone thing. Bush's defiance against his father and desire to prove himself the better man was the most immature and foolish aspect of all. Had he sought council from advisers of previous administrations, most notably his father, he would have been told that removal of Saddam would result in civil war. Perhaps he did receive this council but didn't believe it or just chose to ignore it because of the other factors involved (all the more despicable).
I agree that the diversion from Afghanistan to Iraq was done in large part as a distraction, because it was more tangible to capture Saddam (though not as timely as hoped) than remaining focused on pursuit of Bin Laden. This being the case, Bush has no right to claim he is fighting a "war on terror." Also I believe it was to create a war, thus making Bush a "war president" for purposes of re-election.
One has to wonder whether claims that we'd be welcomed as liberators with flowers, etc. was truly a miscalculation, or whether it was just propaganda to retain the hope and support of the American people (because you see you have to keep catapulting it). The latter is more offensive to me, but I think the consensus is poor planning/execution really existed, as manifested by the looting, etc., though both are unacceptable.
As for a neocon agenda, remember that Bush did not embrace/incorporate neocon philosophy and rhetoric until the invasion began to go awry. Somehow I doubt he really believes it anymore than he is really born again (which he became after losing his first election due to lack of support by the religious-right). How timely it always seems to be when this supposed man of convictions gets his convictions.
The neocon agenda is correct that Iraq is strategic. Public sentiment is correct that Saddam was a menace. But these facts are not enough to justify the loss of life and the cost of millions each day, as well as loss of world-wide respect/relations, etc. I wonder if many neocons will ever come to grips with the fact that other countries cannot be forced to drink the water, and that other cultures must evolve in their own way. And that democracy does not necessarily result in peace, and certainly not necessarily in pro-American sentiment.
Currently the right-wing is whining about how Iraq is the first time the U.S. has forcefully interfered with a sovereign nation (they roll their eyes and use a snide tone when the say sovereign), so the world does not have a right to hate us and call us a bully. While others come right out and say we are bigger and stronger, so why not be a bully? Those are the same people who say intellectuals are the root of all problems, as if it is better to have ignorant people like Bush lead the free world.
Those are the same people who don't know history, let alone a proper understanding of current events. I guess supporting revolutions with arms/advisers, giving/withholding aid or trade agreements versus embargoes, etc., or just indifference toward a country (e.g., Darfur) is not interference. I guess it only counts as bullying when it is a preemptive, illegal regime change.
In the meantime, do you think this most recent announcement will have any impact on people who still believe Iraq was involved with 9-11? Do you think they will say "Bush mislead us"? Do you think they will now know they were lied to and that this is an impeachable offense?