Most people knew that Saddam had chemical weapons, he used them against the Kurds killing thousands, which was well documented at the time. When people talk about WMD's they were using it as shorthand for nuclear weapons. It's amazing to me that most people don't know about the 550 tons of Yellowcake, the pre-cursor to Plutonium, that was shipped out to Canada after the second gulf war.
Rather than a devious plot by Bush to cover it up, I think it was more a failure to go over the heads of the Democrat Publicity machine ( a.k.a. the "Press")