Well, it's kind of difficult to rebuild anew something under the management of corrupt, thieving politicians and their cronies.
Parasites like them can only survive on a healthy host, and for centuries New Orleans was healthy and thriving as a major port city and commercial hub.
Parasites can't build anything themselves, though, that requires productive, self-reliant, confident people without too many parasites sucking their blood while they build.
Katrina threatened to leave the parasites high and dry, with hardly anyone left in town to graft - they've had to resort to swindling the rest of the United States.
Article: Where Did the Katrina Money Go?
Good post, good link.