My favorite historical anecdote that shows what the war was really about is the story of the book The Impending Crisis of the South. It was written by a white Southerner, Hinton R. Helper, in 1857, and it argued for abolition not because slavery was cruel to the slaves, but because he argued it was holding the South back economically. It allowed the slaveowners, who were a tiny minority of the white population, to dominate the Southern states and keep most of the wealth and political power. Therefore, the book was aimed primarily at white Southerners who weren't rich enough to own slaves.
The Impending Crisis of the South panicked the slaveowning class almost as much as Northern abolitionism, and the legislatures of many Southern states, which were of course dominated by slaveowners, banned the book. Three men in Arkansas were HANGED just for possessing it. The rich whites could not allow poor whites could to turn against the system of slavery that their wealth depended on. So where, exactly, was all the Southern money going?
Once Northern troops started moving in on the Southern states, the slaveowning class riled up the poor whites by shouting that their land was being invaded, and they died by the thousands.
So hell yes, the Civil War was about slavery, and it wasn't only the slaves who were hurt by it. The Civil War was about rich white men duping poor white men into going off to die so the rich white men could continue to exploit, torture, and rape poor black men and women. The only credit I am willing to give the slaveowning class is that they were willing to die for "the cause" alongside their ignorant dupes, but that doesn't mean the war itself was any less wrong. As a direct descendant of those ignorant dupes, I am sickened by how my fellow descendants continue to be fooled by the slaveowners' lies.