I think some of them mean well, and then some of them go into the army for an ego boost. But yeah, the Iraq war is insane.
It wasn't insane. The US hit their domestic peak oil in the early 1970's, and now 2/3rds of US oil consumption is met by imports, and domestic production is about half of what it was at it's peak, so the US is critically dependent on foreign oil supplies, and this dependence has been a powerful driving force behind the US foreign policy shift from isolationism to interventionism.
By getting their dick wet in every middle-eastern shithole they can shove it into through force or persuasion, the US has prevented Russia and China from exerting a significant influence in that region and has gained significant leverage in trade negotiations. Their extensive military presence and political influence in these countries will also help them to mitigate the 'Export Land' effect, where an oil exporting country very rapidly ceases exports after hitting their production peak, due to growing domestic demand that overshoots domestic production once production begins to decline.
With Global oil production currently peaking, and well into decline at a regional level in most places, I suspect that the global political situation is going to get pretty ugly as the major players struggle to meet their energy needs. Throw climate change into the mix and the 21st century could make the 20th look civilised by comparison.