I think it was about dealing with a mad man (Saddam Hoisinsane) who demonstrated that he had expasionist ideas, who had used WMDs and who supported and financed terrorism. The fear was that he would furnish terrorists with whatever they needed and sooner, or later we would have to do something about Saddam, or his even more evil sons. Saddam had violated the cease fire agreement we had with him and the myriad of sanctions the U.N. had on Irak. At the time, Iraq was the most pressing threat to us and it just couldn't be ignored.
The overwhelming majority of Congress and the American people favored taking action against Iraq and so did Great Britain and some of the other responsible countries of the world. If it were just a matter of oil, it would be much easier and cheaper to just buy it. If it were just the matter of backing Israel it would have been easier to issue a dire warning that we would view an attack on them as an attack on us and we would anihilate any country that transgressed.
What is so damned hard about accepting this thing at face value? Do we always have to look for ulterior motives?