Basically Saddam was taking a page from the CIA and set up his facilities to do just-in-time production. That way he could have everything there ready to be processed at a moments notice and hand them off to his in-house terrorist group to have plausible deniability. That pretty much fits with what we’ve found.
There’s also numerous reports of things either being destroyed or carted to somewhere else, such as Syria, who is having their own trouble right now. We may find those weapons yet.
They may find us first.