I've never heard of emergency generators that did more than light the exits sufficiently so people can find their way out. The Superdome had them -- until they were flooded out.
So the bottom line is that the problem was an enormous hurricane and an unprecedented, devastating flood.
There were thousands crowded in a dark, unsanitary facility. Thousands that should have been evacuated from the city prior to the hurricane, but the city had no plan for that.
This was an enormous natural disaster. I wish that critics could keep that in mind as they lay blame on FEMA for not doing enough, soon enough.