IIRC, during the morning of 8/29, Blanc-O called the use of the Superdoom "an interesting experiment" on national TV (The Today Show) when asked if the structure would hold.
Also, remember back on Sunday the 28th how much confusion surrounded if and when they would even open the Superdome. I suspect the Mayor and Governor were already squabbling over how to respond.
The locals knew what would happen if they locked up 25,000 people in there. They live with those crazies everyday.