He was supposed to have been the first post-Saddam president of Iraq, since he was a buddy of Wolfowitz and his DoD cabal. Problem was when he marched off that U.S. transport plane in his black fatigues and small security cohort., nobody in Iraq wanted him because he was a crook and a coward.
He didn't control DC which is why he is not solely to blame. Plenty of people inside the beltway at the time were looking for an excuse--similar to what we've been seeing with Syria. He, "Curveball" and others told them what they wanted to hear and they ignored warnings from our Intelligence people about their credibility. All of them are just as much to blame.