My understanding is that it is always known that SH had chemical weapons at one point, but had decommissioned them. What is at those sites are the decommissioned remnants of such weapons that where no longer usable, but difficult to destroy entirely.
I suspect that part of the reason Bush (and Clinton and 0bama) took a soft line on this is that the site might become exactly what it has become, a beacon for nut cases who don't care if they die so long as they can give a weapon to jihad. Even 0bama stopped bleating about it when he started attending the briefings. Is the stuff usable? Probably not. Is it safe? Absolutely not.