The President has given consistent reasons for invading Iraq from beginning to end. In short, take out a dangerous regime and replace it with a state that upholds the rule of law as part of transforming the Middle East.
The legal and moral bases for regime change were always unassailable and nothing has changed. WMD were cited as what was assumed to be a slam-dunk to curry support. The world's elite with such tremendous unity that it cannot be ignored has behaved ever since (I would say tendentiously) as if WMD stockpiles had been the only justification, and they will move the goalposts as much as they can because they think damage to US credibility is a good thing.
For Saddam, there was available a transparent way of disarming which other countries such as South Africa have shown. But Saddam's Iraq wasn't capable of it, and now they are gone. Good riddance to one of the worst regimes on the planet. The world in each region needs to hold countries with emerging capabilities to standards. The heightened 21st century danger of weapons and terrorists will not be addressed until it becomes the norm for emerging countries to uphold the rule of law and govern in a reasonably non-oppressive way.
With all that as background, my response to your post is that the President can't force the elites to see the bigger picture. He could not ignore the drumbeating about lack of WMDs, and chose to concede ground. History will be the judge.
All excellent overt reasons for dealing with Iraq. But as current events have shown, the larger strategic value of having large forces in Iraq -- right next to Syria and Iran -- cannot be ignored.
From a long-term strategy perspective, it has become obvious that something has to be done about the dangers posed by Islamic governments in the Middle East. It will inevitably mean military action. We had to grab a bridgehead someplace, and Iraq has a wonderfully strategic location for that, which just happened to coincide with the fact that Saddam's Iraq needed dealing with anyway.
bttt