There IS an NFL game Sunday. Today is my 60th birthday, and my two adult sons are taking me to the Falcons vs Redskins on Sunday as my present.
While it's true that GA Dome crew has OFTEN "turned around" the Dome from college to pro overnight (Sat to Sunday), but to host TWO college games on that field in ONE day, and the added security, etc, I just don't see how the city of Atlanta was going to deal with that. I bet it was never even considered. Plus, FWIW, it's GA State's Homecoming, and they've got events planned before and after the game as well.
And remember, if those who are suggesting ATL because the USC fans could make it, well, I imagine most of their fans in SC (I'm sure they do have a lot in ATL metro area, but still . . . ) wouldn't be able to make it. They're still dealing with flooded houses and loss of everything, esp those that don't have flood insurance. Football is the last thing on their minds right now.