Self-determination for the "right" to hold slaves. Gee, do you think that might just be why they lost? The inherent contradition in such an action? Self-determination for me but not for that slave over there?
The border states didn’t hold slaves and they stayed neutral until Northern troops were sent south to end the secession.
So yes - the side fighting for self determination lost.
It wasn’t over that.
In which case, you can hold the same argument about the RevWar. They ALL had slaves (including “Yankees”).
BTW, a civil war is just a revolution in which the insurgents lost.