I understand there were mistakes on the ground the biggest I consider the CPA and Bremer, but I still think the bigger mistake was setting up the public to think that such a massive change could be done quickly and cheaply.
Obviously the administration was led to believe that there was a "there" there, wheeras there was simply a vacuum of authority. My suspicion is that State and the CIA peruaded Bush not to install an exile government that would have provided something like authority in a revolutionary situation. I believe some sort of Iraqi government could have filled the vacuum, like the 26th of July Movement filled the vacuum in Cuba or, more relavantly, like Degaulle fill the vacuum in France in 1944. Whatever. I do know that in the summer of 2003 that the only authority there was the American army and that the follow on forces, which included my son, were not numerous enough to fill the vacuum.
Why the original invasion force did not remain longer is something that escapes me.