There was work done to the stadium's electrical system back in December, in which feeder equipment connecting the stadium to Energy New Orleans was replaced, but that doesn't look to be related. The manager of the Superdome has said that the incident was caused by an equipment error, not a human one. There's speculation that all the extravagant lights of the halftime show played a role in the power going down, but according to the manager, the show used its own generator and not the stadium's power.
When the power first went out, a friend who I was watching the game with half-jokingly remarked that notorious hacker group Anonymous was behind it. Lo and behold, Anonymous has since taken credit for the attack and multiple people have suggested that they were sending a message related to FEMA's fumbling of the Hurricane Katrina some years back. Is Anonymous really behind it? Only time will tell and it will be interesting to see if the Superdome management places the blame somewhere else in an attempt to discredit the hacker group.