The Civil War was a cultural war led by political incompetents who knew only bloodshed rather than negotiation. A simple solution for ending slavery would have been for Lincoln to use the federal treasury to purchase the freedom of each slave, however, it was nothing short of Northern liberal hate that ensured there would be no peaceful solution.
In their ignorance they fought and died (often bravely) in a cause which was against the concept of Christianity and the ideals of their nation.
In this they are not alone. Germans died fighting for Hitler and Russians for Stalin when their interests were no greater than the poor dumb dirt farmers from the South. But they believed their leaders lying propaganda, too.
Lincoln could not have purchased the Slaves of the south either. There was no ability to afford it from a treasury of 1860s U.S. government. But never got the chance since the whackjobs of the Slaveocracy attacked U.S. interests, property and armed forces forcing an armed response.