What was the reasons for Sherman's march through Georgia?

Answer 1

To destroy the farms and railroads that supported the Confederate armies in the field. He believed that this would end the war quicker than direct combat.

It was also a chance to break free from his long and vulnerable supply-line, and live off the land, following a good local harvest.

Finally, there was a punitive element - bringing it home to the arrogant Georgians that they made a big mistake in seceding from the USA.
To be able to live off the land, and forget his increasingly long and vulnerable supply-line.

To wreck farms and railroads, in order to help starve the enemy troops in the field and damage civilian morale.
Sherman's march through Georgia had two separate purposes.

During the Civil War the Union had blockaded many Southern Ports preventing the importation of war supplies. The Confederate States discovered they had resources to sustain the war without importing anything. The sixty mile path of destruction destroyed factories within that area and prevented transportation across that area. All the railroad tracks were destroyed. It would be difficult to divert materiel to horses and wagons because no fodder for horses existed for 60 miles.

Also, while the men were fighting the war the women performed an excellent job of managing the farms. They supplied the troops in the field with food and clothing. The women favored the war just as much as the men. The march through Georgia announced to the women they could also suffer from the war. They needed to stop supporting it and to discourage their men from fighting.

Thus, it had a twofold purpose.