It could have been both...there was probably a heck of a lot to move in a short period of time...since they didn't know for sure when the US would invade..
Also, remember there were Russian officials still in Baghdad the day we invaded...and they barely got out.
I am sure they were trying to get rid of the evidence of their complicity in the WMD program and move.
Yes, I recall that story. Russian military advisors were detained (by either us or the Brits, can't recall which) with a carload of files they were spiriting out of Iraq.
"A lot" is open to question. Saddam was playing hide and seek with the inspectors for years. Any capability he had would have been designed from the start to be small, concealable, transportable and, in an emergency, disposable. The supporting organization would have been structured for concealment, removal, and disposal operations on short notice. That would mean they kept the stuff pretty much packed and ready to go and only broke it out when they were actively working with it. A practiced team could probably move a small scale chemical or biological unit faster than I could clean out my basement.