Iraq did not spontaneously opt for disarmament. They did it as part of a ceasefire, so they were forced to do it, otherwise the war might have gone on. So the motivation has been very different.
Hans BlixThe inspections started in 1991, right after the Gulf War. One of the conditions for the ceasefire was that Iraq had to do away with all of its weapons of mass destruction - biological, chemical and nuclear weapons and long-range missiles.
Hans Blix