The people behind Iraq invasion were all part of 'Project for a New American Century' which promoted 'Pax Americana' in the Middle East, i.e. a stabilizing occupying force, probably the overthrow of Iraq and Syria.
They envisioned Iraq being a little more like Gulf States i.e. more stable, allies, and a buffer between Israel/Iran/Saudi Arabia.
And some nice construction contracts for Bechtel.
And a geostrategic signal of power.
The WMD thing was a populist narrative justification, the real motivation is literally published for all to see, it's just not what the media war was fought over.
Nobody ever fought a war for purely altruistic motives, it's unlikely the Americans were to have joined WW2 unless they were at risk themselves, but that doesn't mean there can't be motives and actions that are better than others.
Weirdly, the justification for Iraq I think would have been entirely function of historical revisionism given the success or failure. If Iraq was more stable and prosperous then 'it was the right thing to do', if the invasion was a failure, then it 'was a mistake' and that's it. Iraq has $5K/USD per capita GDP now, it has a government, elections, there's progress. Iran has a lot of control and of course Kurds are doing their own thing, but there is baseline order. 'Was It Worth It?' is another question, maybe in 50 years we can understand definitively what the real cost of finally getting rid of a Saddam-like institution was.
[1] https://www.sourcewatch.org/index.php/Project_for_the_New_Am...
[2] https://en.wikipedia.org/wiki/Project_for_the_New_American_C...