I miss the kinder, gentler days of government when the worst thing a president would do is get a blowjob, or lie about the pretense for a war, or wear a tan suit.

A big part of it is that Sadam barred weapons inspectors and generally hinted at it to his own people. And intelligence operations operate off of surprisingly normal hearsay.

The funny part is he was doing it in fear of Iran who had been letting inspectors into half their nuclear program and just hiding the other half (a much better strategy if you have anything to work with).

He even stated that he tried to make his own generals believe they were working on it according to an interview with McConnell. And they combined that with him using previously banned weapons (nerve gas) and being the kind of leader that does shit like this: https://en.wikipedia.org/wiki/1979_Ba%27ath_Party_Purge and https://en.wikipedia.org/wiki/Dujail_massacre

On the bright side, he was a pretty decent nazbol leader by that region's standards if he wasn't actively trying to kill you and everyone you know.

Some of Saddam's generals thought he had WMDs. It wasn't a completely smooth brained take, but it was way too flimsy for going to war.