Hanson gets that one correct. This is, in fact, one of the two biggest Second Guesses surrounding the two Gulf Wars (the other one being breaking up the Iraqi army after the fall of Baghdad).
Personally I lay this one at Powell's door but I see where he was coming from. He was and remains an internationalist with a strong belief in collective security, and his principal motivation for the ceasefire was the maintenance of the coalition and the UN sanctions under which it operated. It was a sound political and diplomatic decision (the political and diplomatic missions were, after all, accomplished by the ejection of Saddam's forces from Kuwait) and a disastrous military one.
A consideration of his performance subsequently as Secretary of State will confirm this set of priorities. It is a perfect example of a failure of transition between tactical and strategic thought. IMHO, of course - I'm no Colin Powell fan but hindsight is 20/20.
Remember also that Colin Powell was a national security advisor type. He never commanded any unit larger than a battalion in the Army [if I recall correctly]. One of the risks when you promote a DC insider over combat soldiers.
Powell could have maintained the coalition and the UN sanctions and still destroyed the Iraqi Republican Guard on the ground in Kuwait and on the border. Powell was motivated more by not killing anymore Iraqis than geopolitical concerns. It was like shooting fish in a barrel.
Personally, after touring the highway of death by air via helicopter and on the ground plus going through the burning oil fields, we had the perfect excuse to go after Saddam for war crimes and an environmental catastrophe. By allowing Saddam to stay in power and his elite forces to escape, we were sowing the seeds for the next conflict. That said, the coalition's objective was to eject Saddam from Kuwait not to remove him from power or occupy Iraq. Doing so would surely have had repercussions from the arab members of the coaltion and for reasons know now, Russia and France would have objected vehemently.