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 nerve agent VX is one of the most toxic ever developed. 13,000 chemical bombs were dropped by the Iraqi Air Force between 1983 and 1988, while Iraq has declared that 19,500 bombs were consumed during this period. Thus, there is a discrepancy of 6,500 bombs. The amount of chemical agent in these bombs would be in the order of about 1,000 tonnes.
Hans Blix