Can you blame them? Who could have war gamed Iraq into Vietnam V.2, including the rats de facto aiding and abetting Al Qaeda for domestic political gain? Nobody could have planned an adequate Phase IV of the invasion of Iraq in which everything that could go wrong did go wrong, IMHO.
Any of the old SF guys would of. The Brits, for hundreds of years were good, very good. Post WWII, not so much.
There was no, zero, zip post reaching into Baghdad planning. The Army thought that State would handle it. The WH and State, thought the Pentagon. No one was fired.( Bush’s never fire anyone )