The "great man" theory of history has been out of fashion for decades. Historians trying to explain the course of human events point to geography or climate or technology. They explore the everyday life of ordinary people and the tides of change that sweep through whole populations. When they write about individual historical actors, the emphasis tends to be on psychology. Kings and Queens, Presidents and Prime Ministers may affect events at the margins, but the notion that history happens because someone decided it should happen is regarded as unenlightening if not simply wrong.
About Gulf War II and its consequences (whatever they may be), though, the "great man" theory is correct, and the great man is President George W. Bush. Great in this context does not necessarily mean good or wise. It does usually suggest a certain largeness of character or presence on the stage, which Bush does not possess. Whatever gods gave him this role were casting against type. But the role is his. This was George W. Bush's war. It was the result of one man's deliberate, sudden and unforced decision. Yes, Saddam Hussein deserves the ultimate moral blame, but Bush pushed the button.
Bush's decision to make war on Iraq may have been visionary and courageous or reckless and tragic or anything in between, but one thing it wasn't was urgently necessary. For Bush, this war was optional. Events did not impose it on him. Few public voices were egging him on. He hadn't made an issue of the need for "regime change" during the presidential campaign or made it a priority in the early months of his Administration. If he had completely ignored Iraq through the 2004 election, the price would have been a few disappointed Administration hawks and one or two grumpy op-eds. But something or someone put this bee in his bonnet, and from a standing start, history took off. Thousands died, millions were freed from tyranny (we hope), billions were spent, a region was shaken to its core, alliances ruptured, and the entire world watched it all on TV.
Compare America's other wars of the past 60 years. All of them had, if not inevitability, at least a bit of propulsion from forces larger than one man's desire. Gulf War I was provoked by an actual event: Iraq's occupation of Kuwait. George the Elder didn't have to make war, but he had to do something. Vietnam, famously, was never an explicit decision. Even the parody war in Grenada had a few captive American medical students to force its way onto the agenda. Some people believe that Franklin Roosevelt personally, deliberately and even dishonestly maneuvered a reluctant America into World War II. But World War II was history boiling over and impossible to avoid one way or another.