Most of the time it was some religious conceit, like the south still has Christianity therefore they won. It often came down to shifting goal posts or concepts not related to the goals of the confederacy. Like I was told the goal of the north was to make whites into slaves for black people, or to completely erase the southern states, or to eliminate Christianity. These goals weren't accomplished, so this gets spun into a victory for the south somehow. Reminds me of how current day liberals will claim Ukraine is winning because the entire country isn't annexed, even if that wasn't Russia's goal