Our main reason for helping Saddam gain power and keep him there by supplying him with so much aid, military and otherwise, was to counter a powerful Iran. When Saddam went to war with Iran, the US sanctioned and encouraged it. Eight years and a million dead later, the two nations were still stalemated.
That ended our 'influence by proxy nation' policy, which began with the installment of the Shah. We had been 'screwed' by both Iran and Iraq at that point. A more direct US influence in the region was 'needed'. Hence, Gulf war I and II, brought to us by Bush I and II.
The result, predictably, has been an out and out foreign policy, security, and humanitarian disaster. Ironically, now we're being screwed a second time by both Iran and Iraq, and our influence in the region is, shall we say, tenuous.