The South lost because they lacked the political power to keep the law on their side (new states all becoming free States, congressional numbers never adding up for them, president who actually dislikes slavery, etc) and then they didn't have the economic power and monetary flexibility to maintain a successful revolution. It's interesting that even with the relatively primitive weapons they had on both sides, the south couldn't make what they needed and had to go into massive debt to try to import everything. Not to mention that cotton from India was lowering the market price and no one in their right mind would buy a confederate bond. They had basically no fucking right to expect it could turn out well for them.
Even though they had no chance, I think burning farms and cities was just a way to prevent them from gathering more money to buy more guns and supplies and overall it was just a way to prevent more bloodshed. I just love how it shows the one time that you can say the second amendment was actually used, it totally failed and that was with the simple weapons back then. Hitler made a similar mistake in trying to give his soldiers the best weapons and not consider how unmatched he was in industrial output versus the USSR and America. I think his initial estimate of the number of Soviet tanks was like one tenth of what it actually was.