The original plan was to keep the Ba'athist government intact. Then Paul Bremer and CPA decided to expel everybody from the government. All of sudden, you have 100,000 unemployed young men who have nothing better to do with their time.
What I noticed at the time was no one could state the definition of mission accomplishment there. Invading Iraq was a colossal mistake. To think those people were going to “welcome” American troops on their streets was idiocy.