Saddam Hussein had been playing a game of pretending that he had WMDs throughout most of the 1990s up to the Iraq War. The US intelligence community took those claims too much at face value, and when the UN inspectors went in to evaluate the evidence, they didn't say that Iraq had no WMDs, they said they couldn't find evidence of WMDs but the Iraqis were being too shifty to draw a firm conclusion. Unfortunately for Saddam, the Bush administration took this only reinforcing earlier beliefs that Iraq was fundamentally untrustworthy and hell-bent on WMDs, and was willing to go to war even without rock-solid evidence (unlike the EU, which saw the lack of evidence as a good reason to do nothing).