That wasn't exactly mass deception. It was basically group think inside a certain administration, supported by an at that time must-keep-in-sync-with-them UK prime IIRC. Most of Europe had access to more information and knew it to be incorrect (there were investigative TV programs etc showing why). Most people actually believed that the WMD claim was just a stunt to make an excuse for going in and finally finish the '91 war. It certainly wasn't a global conspiracy by scientists in any sense.