Sherman’s army didn’t travel through or occupy Athens. In the Battle of Atlanta, his army came from the North. In the March to the Sea, his army departed in a south east direction.

Regardless, not everything was destroyed in the March to the Sea. Savannah is an example. It was not damaged at all. Sherman’s general rule was to burn only buildings and materials that were of military value that the Confederacy would regain control after Sherman passed through.

So, as an example, he departed Atlanta and basically gave it back to the Confederacy, but he destroyed everything of military value so it was of no benefit to the Confederates to reoccupy it.

His other general rule was to destroy towns that didn’t submit to the Union army. Towns that didn’t fight were generally spared and towns that engaged in a guerrilla resistance were more heavily damaged. Many towns were completely spared. After the starving POWs from Andersonville was discovered, Sherman ordered an entire town burned down.

The March to the Sea was about 60 miles wide. At every edge of his main army he had foragers who carried out much of the activities. Not everything was under a direct order from Sherman. Troops picked and choose what to take and destroy based on orders plus what they were allowed to get away with.

The university of Georgia had no military significance and the town of Athens didn’t engage in armed resistance to the Union troops due to the movements that occurred. So it didn’t qualify as the type of building Sherman would order to be destroyed.