From what the Secession Commissioners, whose job it was to explain why the states had seceded & encourage others to do so, said on the subject, the reasons for secession are very straight forward.I hesitate to add anything to the discussion, once about what accounted for the ferocity of white Democrat opposition to the exercise of voting rights by freed people, who in spite of their fondness for the many kindnesses and blessings bestowed on their carefree existence by their owners, were quite accurately perceived at the time as a large block of Republican voters that would allow "scalawags" and "carpet baggers" to attain electoral victories and thus undermine good old local "home rule" if, in fact, the war was not about slavery after all?
In the 1970s, social history made large inroads in just about every field of historical inquiry. Perhaps nowhere, however, was it more influential than in military history. So the vast majority of Civil War military history is above all concerned with the individual experiences of "Johnny Reb" and "Billy Yank." We learn from such an intimate examination of the everyday, ordinary soldier-level experience that these were young men who were bounded by ties of kinship to their fellow comrades in arms--"bands of brothers" to reuse that term. Their diaries, letters, etc. do not indicate that they shared the same understandings of what "the war was about" that, say, the respective national leaders did. Personally, I'd rather read accounts from that level. On the other hand, a steady diet of such books has effectively blurred the overarching politics of the war. "Why were the armies in the field fighting one another?"
So while we know that Southerners were fighting for home and hearth, and that their identifications and kindred were intensely local, and that "loyalty" to the region, and by extension, the state loomed larger than identification with the entire nation, this has the effect of erasing what precisely caused the war?
Rhetorically, Secession Commissioner Benning of Georgia asked the Virginia delegates, "What was th reason that induced Georgia to take the step of secessioin? That reason may be summed up in a single proposition. I was a conviction, a deep conviction on the part of Georgia that separation from the North was the only thing that could prevent the abolition of slavery."
I take Justice Benning at his word as the official spokesman for the state of Georgia.