That's the point. That's why they were here in the first place. I highly doubt they were here flipping burgers. Saying WMD Experts were/are in Iraq to do anything other build WMD is like watching a guy in a mask with a gun walk into a bank and then assume he's only there to cash a check.
Not really. We know that Iraq once had WMD, and the people that could make them, maintain them and decommission them. When Hussein stops building WMDs - the expertise doesn't evaporate; they still live in the country.
The insurgents are smart enough to realize this, and they are now looking for these people with a view to employing them (or otherwise persuading them to use their expertise).