We went into Afghanistan because the Taliban harbored the organization that committed 9/11 and refused to turn them over.

We went into Iraq primarily because a group of Neoconservatives were drunk on the unipolar moment and believed the US could spread democracy at the barrel of a gun and remake the Middle East. Haliburton definitely made money in Iraq, but we did not go in for oil.

The invasion of Iraq was based on the fact that Bush and Cheney were neoconservatives, which means essentially liberal Trotskyites. They believed that human rights were universal and it was legitimate to uphold them by force. So in their logic, Saddam Hussein was a bad a guy and Iraq was a good candidate for showing that the US can start rolling into places and giving the people their freedom, just like that.

The basic assumption was that stable democracies grow on their own once you get rid of the dictator. So show up to a country, get the dictator, rinse and repeat. Now you have nice democracies all throughout the world. In that view, not invading is immoral because it means you’re condemning millions of Iraqis to live under Saddam’s dictatorship.

The basic lesson from this is that countries don’t act out of material self-interest as much as armchair cynics assume. Instead they’re frequently operated on an emotional or ideological basis.