Because he moved them to Syria to avert attack.
Even if that were true — and Cheney publicly said it’s not — they were never any threat since Saddam never intended to use them; he shipped them out of the country instead of using them to defend himself, according to the neocon fairy tale that you’re buying.
Actually, I was buying the "neocon" military aerial photographs, showing the trucks and actual materiel evacuation, all done while the moslem UN was frigging around, giving him plenty of time.
Then, of course, just as ISIS was about to commandeer them in Syria, Putin had to step forward to "destroy" them.