People assume that they know what would have happened if different decisions had been made. But no one knows what would have happened if President Bush had made different decisions. The situation could be far worse now if the course advocated by some had been followed. They don't know, they just assume that they know. Things ain't so bad now.
As Shiite/Persian Iraq tries to gain influence in Iran, we use that to our advantage.
We gain support among the Sunni Arab states to move against Iran. As this happens we gain support with Arab Iraqi Shiites of Najif against their rivals the Iranian Ahiites of Qom.