You're missing the point.
No. I get your point. You wish to excuse the failures of Mayor Nagin because other people didn't cooperate with him. You're simply wrong. There is no excuse for the chief executive of New Orleans, the person with the ultimate responsibility for everything that happens within his jurisdiction, to have failed so utterly.
Other people didn't cooperate with him. In a disaster involving the survival of tens of thousands of the people you are responsible for you have those uncooperative people within your jurisdiction arrested or, "in extremis," shot.
What you don't do is whine about it on TV, particular if you are not willing to then cede your authority to those you want to come bail you out.
You can't say "save me, save me" and then claim that your saviors have to get permission from you for every decision they have to make to do the job.
I've been in charge of emergency scenes. You're either in charge or you're taking orders. He wanted someone else to take the responsibility, but he wanted to be in charge. Doesn't work that way. I had a knock down drag out fight (legal) with a city cop over precisely that issue at an accident scene I responded to as an ambulance driver. Under New York law the senior medical personnel is in charge of patient care at an accident scene (or was under the "good sam" laws in the mid 70s). I won. The cop ended up losing his job (not directly over that incident, but it was the next to last straw).
It is absolutely true that, in an emergency, you lead, follow or get out of the way. Nagin did none of these things and people died.