Distracting people with the oil excuse gives cover to ppl who need it least.
The most salient motivation was (perceived) security. The US government was absolutely paranoid after 9/11 and they really did not want Saddam to continue ruling in Iraq.
And in pursuit of their noble goals, somewhat paradoxically (in the untrained eyes of the naïve observer) they resort to bombing the infrastructure, destroying all state institutions, including education, and also loot^H^H^H securing the national cultural heritage (to preserve in custody in private collections in the City on the Hill). Actually, their belief is so strong that 20 years later the infrastructure still isn't rebuilt (except for oil export, but that's not what it's about).
Ill-intentioned cynics will question the motives of these nation builders and judge them on the merit of their results, not on the holiness of their belief. They will point out that the ped^H^H^H … actually doesn't really love children, but acts in pursuit of highly selfish goals.