Bush didn't lie, he was wrong, as was everyone that advised him, including most members of the opposition. Saddam stated (before his neck was stretched) that he complied with the UN to stave off the US, but then engaged in ruses to make the Iranians think he still had WMD because he feared them. The US (and the world), engaging in an extreme case of Western centric thinking, never understood that Saddam might really be more worried about Iran, a country with which they had a REAL war with REAL casualties, than he was about the US. Ref:
http://english.aljazeera.net/news/americas/2009/07/2009738433344267.html
(I picked the Al Jazeera story, but it can also be found on MSNBC, and other actually credible websites--I just picked the ones favored by the left for emphasis.)
Saddam miscalculated, and Bush was wrong. So was everyone in the US intelligence community, and most of the world's intelligence services as well. Life is too complicated for demagogues to understand.