From: Pete Mansoor (edited)
Three decisions in the spring of 2003 created the insurgency in Iraq:
1. De-Ba'athification. Many Iraqis believed it meant the de-Sunnification of Iraqi society
2. Disbanding the Iraqi Army. It was the only local that could have been used to secure Iraq after combat
3. Empowerment of an Iraqi Governing Council composed of highly sectarian politicians, many of them expatriates who did not understand the Iraqi people's concerns
After WW2, Germany was devastated from end to end and its armed forces annihilated. Millions of Germans died in the war and the Germany people were starving. Simply put, the level of distress made the Germans more open to cooperating with the occupying forces.