Stauber and Rampton offer the best explanation to date. Unlike Blair, the Bush team never wanted to present a legal case for war. They had no interest in making any of their allegations about Iraq hold up to a standard of proof. The real effort was aimed at amping up the mood for war by using the psychology of fear.
Facts were never important to the Bush team. They were diposable nuggets that could be discarded at will and replaced by whatever new rationale that played favorably with their polls and focus groups. The war was about weapons of mass destruction one week, al-Qaeda the next. When neither allegation could be substantiated on the ground, the fallback position became the mass graves (many from the Iran/Iraq war supported by the US) proving that Saddam was an evil thug who deserved to be toppled. The motto of the Bush pr machine was: Move on. Don’t explain. Say anything to conceal the perfidy behind the real motives for war. Never look back. Accuse the questioners of harboring unpatriotic sensibilities. Eventually, even the cagey Wolfowitz admitted that the official case for war was made mainly to make the invasion palatable not to justify it.