VIA the CIA’s intel; other Intel agencies had not investigated to the same degree, they didn’t have their own agents in the field as the CIA did.
Spain, Germany, who were the two major players that engaged in parallel investigations that concurred with the CIA’s conclusions, were basing their case on what the CIA field intel told them. They didn’t consult a different source.
This turned out to be critical, as the CIA had… “embellished” their intel, likely out of a desire to appear on the ball after the terrible oversight 9/11 had been for them, and had resulted in their losing their position as the head of American Intelligence community.
raq had WMDs and was prepared to USE them when the US went back in in 2003
Which wasn’t true of course.
Saddam was a chronic liar, and here, he was lying for the specific purpose of deterring an invasion by the Iranians. The Iranians had clear ground superiority, even before 1991, and were still holding grudges from their last war. Afterward 1991, Saddam was left in a tenuous position where even the Kurds could make consistent challenges to his authority, openly engaging in relations with the Iranian regime.
Saddam let his inner circle know that he didn’t have these weapons; and he lied to everyone else, even his own staff who he knew were providing Intel consciously or unconsciously to his enemies, both within and outside of Iraq.
Saddam was also a tad… conceited. He didn’t believe for a moment we would invade, and even as we did so, he didn’t believe we would take over and boot him out of office.
This is why he didn’t burn his oil wells in 2003, and why he didn’t commit his whole force from the start to fight us. He was planning for the post-invasion where he thought he would be left to once again re-build his regime.