if one insists on a simplistic answer to this complex question (and only simpletons want/need simplistic answers to such questions), let it be this:
southerners wanted to be FREE from a government that they believed no longer was interested in their rights & best interests. i.e.,it was precisely the same cause as the American Revolution.
free dixie NOW,sw
Exactly right. For "rights and best interests" read negro servitude. If it had been any other issue it wouldn't have taken a century for the southern black man to acquire the same civil rights as everyone else ... and that at the hands of the hated "federal" government.
If the average southerner (for whom slavery wasn't an issue) had had any sense he would have liberated himself from the southern aristocracy before tackling the bigger projects.