There's that public school education rearing its ugly head again.
The Civil War was fought over state's rights. Slavery was merely an exercise of those rights.
"The new constitution has put at rest, forever, all the agitating questions relating to our peculiar institution
African slavery as it exists amongst us the proper status of the negro in our form of civilization.
This was the immediate cause of the late rupture and present revolution. Jefferson in his forecast, had anticipated this, as the “rock upon which the old Union would split.” He was right" Vice President, CSA, "Cornerstone Speech"
?Corner Stone? Speech | Teaching American History
Slavery was really an effect, not a cause of the civil war. While as I pointed out to House boiling the war down to one factor is ridiculous, the big three are state rights, economics and slavery and you cannot separate those, they are intertwined. I said for that reason that slavery was a "big" reason, it was. So was State rights, as House said.
Again, you cannot separate them, but if you want to order them, you really need to go to disease, symptom and solution. You could argue the proximate cause of the war was slavery. However, that was a symptom, the South did not want slavery for slavery sake, they needed it. Why? The North was industrializing, the South was agricultural. The North for that reason was drawing population far faster to fill the factories. Not needing slaves, they found it reprehensible. So the reason the south wanted slavery was economics, that was the cause, slavery was the symptom and therefore economics and not slavery drove the war.
Clearly State Rights tied into that as well, but that was not the cause either. As the North and South changed economically and culturally because the North was drawing population and immigrants faster and the North became more powerful, the South resisted being forced to follow the path and the direction of the North. Hence, the solution to that was "State Rights." Again, they did not want State Rights for it's own sake, they wanted State rights to protect their economy.
They needed slaves to support their economy. Therefore, the primary reason for the war was clearly economics. State Rights and Slavery are inseparable from that. But they were not the goals in themselves.