You are forgetting that both Political Parties voted to invade Iraq, Democrats found the evidence of WMD convincing at the time. Saddam Hussein himself boasted of having WMD. We also know that convoys of trucks with tarp-covered freight poured across the border into Syria just before the US invasion. The simplest explanation is that the Sarin Gas and the equipment for its manufacture were shifted to Syria ahead of Desert Storm.
The “outright Lies” explanation is a piece of rewriting History to make the Democrats look better, but it doesn’t wash. Clinton voted for War.