The reasons for the war themselves were questionable from the get go. Bush Sr. wanted to believe the Iraqi's would kick out Saddam on their own, but most people are afraid for their own skins and unwilling to stand up to someone dictator or not, who has his own personal army.
Bush Jr. kicked the UN out as they toured Iraq and were not finding the weapons of mass destruction. Since the UN didn't finish their inspection, it always left that small margin of doubt that they just didn't get to where the weapons were hiding.
To be fair, in the first Gulf War, there was plenty of evidence supporting the development of Gerald Vincent Bull's "Supergun", with ballistics capable of hitting any American city.
http://en.wikipedia.org/wiki/Supergun
Transcript of a documentary during Gulf War 1;
http://www.pbs.org/wgbh/pages/frontline/programs/transcripts/911.html
The mismanagement came from a clear conflict of interest on Cheney's part with Halliburton, and Rumsfeld's attempt to appease public opinion through his insistence that the war needed a minimal number of troops, money and time, against all military advisors clear disagreement.