Forget about oil, forget the evil-dictator thing, forget about the intricacies of middle-east politics. All you have to do is take one look at the Saddam In His Tighty Whities photos to see exactly why Bush has such a problem with him. "Who do you think you are, Mister Big Stuff?"
Personally, I think he's packing. Which wouldn't be surprising, since Bush is the sort who'd be intimidated even by a rolled up sock.