Atlanta airport is massive. You often fly in alongside other planes landing on different runways. And if you have to connect there the distance between terminals can be massive. Once it took us an hour to get from one side of the airport to the other meaning you are susceptible to missing your connection; your baggage is offloaded but miraculously you and your luggage gets to its final destination with relative ease. If you miss one connection just catch another as Delta seems to have capacity to take passengers who missed their allocated flight.