This is right on the money:
"Bremer's most fateful decision was to essentially ban all former Ba'athists from participating in the Iraqi government, and to disband the Sunni dominated military. With a few swipes of his pen, Bremer sent tens of thousands of Sunni Muslims into the street. Many were armed, trained, and then no longer invested in the new Iraq. Some of these disbanded soldiers and government officials would later form the core of the Islamic State."

The ugly truth is we sanctioned the social disintegration and kept the ones who really could,would, and had a vested interest in fixing it, from fixing it.

It is most sad that we let the most corrupt elements of their society take charge and stopped the natural counterweight the Ba'athists provided that society. In our ignorance, we unconsciously picked winners and losers. Who better to help the military than a military who knew the landscape? Now the World is the worse for our hubris.
Excellent post.