The Union took advantage of the Southern weakness to win the war because the Confederacy depended on many imported goods, and since the North controlled the navy the seas, the South got suffocated by the lack of imported goods such as gunpowder that was needed for the war.
Also, the Southern States had just a few railroads, different than the North, this also made it harder for the Confederacy to transport food for soldiers and civilians.
When the Union used the “total war” philosophy, they used this weakness from the Southern States to win the war, by destroying civilian structures, cutting off food supplies and others.