This quote from the article explains why:
"Saddam, it says, even fooled his own military chiefs into believing that he had WMD. This was designed to deter uprising from rebel Iraqis, on whom he deployed mustard gas in 1988, and aggressors in the Middle East."
Since when are rebel Iraqis and aggressors in the Middle East a greater threat then the combined military forces of the Free World ? A threat of invasion from the greatest military the world has ever seen was a far greater threat to Saddam then any thing else. The ease at which that military threat disposed Saddam from power was evidence of that fact. Days to Baghdad. Not weeks or months. On the eve of invasion Saddam should have been 'coming clean' on having no WMD. He did not.