I will be the only one to answer my own question
Moderators, merge it with brettig thread if you want to...
Thinking out loud...
I can only guess what is behind the curtains. Many reasons for this war have been cited.
Some of the arguments USUALLY mentioned by anti-Bush, anti-war people.
One is that it's all about oil. Of course, US needs cheap energy supply to give a boost to its stagnating economy. Though US companies will not be able to refurbish Iraqi oil wells and begin production of oil rapidly... but it will be enough to stabilize world oil prices at the level acceptable for the US economy. Can it be the only reason for starting this war? Only one of them...
Another is that some people in US administration have personal interests in this war. No doubt Cheney's Halliburton will make lots of money in the post-war reconstruction of Iraq but one can hardly imagine in earnest Cheney dictating to "ignorant" Bush: 'It's time to bomb Saddam'. Personal interests are there but they are not enough...
Another reason (often cited in my country, partially has to do with the 1st one) is that US now is a 'loose cannon' which has lost its only counterweight in the Cold War. With no one to oppose it seeks to establish its dominance in the world. First, it will be Middle East and control over oil reserves there. Everyone who opposes it, will share the fate of Iraq...etc. Many ppl call it "America's geostrategic goal". I will not comment on that.
Some of the arguments USUALLY mentioned by the war supporters.
1. It's about disarmament. It's highly probable that Iraq has WMD, at least bio- and chemical weapons. It's impossible to make it disarm through UN inspections. 12 years of Saddam playing tricks with the world community etc.
2. Iraq is a threat (if not to US) to its immediate neighbours. Saddam attacked Israel, Kuwait and Iran.
3. It's about regime change. Saddam's the worst tyrant living on Earth, killed thousands of his own people, gassed Kurds. That's intolerable. We remove Saddam, help Iraqi people choose a democratic government, then democracy will start spreading in the region cos ppl there will understand it's much better...
Actually all three mentioned reasons are interrelated. It's all about Saddam.
In my modest opinion ALL the abovementioned reasons together could not be enough to make the US start this war.
There is another, principal one that I omitted intentionally. Yes, whatever u call it: '9/11 aftershock', 'US security concern'...
But it needs a special post.