Just read the original article of succession from South Carolina. At the start the South said it was about slavery and the North said it was about preserving the Union.
Confederate States of America - Declaration of the Immediate Causes Which Induce and Justify the Secession of South Carolina from the Federal Union
https://avalon.law.yale.edu/19th_century/csa_scarsec.asp
Lincoln did not make ending slavery the basis of his call for troops after Fort Sumter, because he did not want to drive the other slaveholding states (especially Kentucky and Maryland) into seceding. He might have had much less success in getting volunteers to fight if he had announced abolition of slavery as the goal.
Most of the Confederate soldiers were not slaveowners. Why were they willing to risk their lives for the Confederacy? Most of them believed it was their duty to defend their state from the Northern invasion. But not wanting to be in the same country with the Yankees may have been part of it.
At the start the South said it was about slavery...
What’s interesting is that slavery was actually going away on its own. It was becoming too expensive and many of the menial jobs they did were becoming automated.
And the solution the north brought after the war only kept them oppressed. I especially find the “40 acres and a mule” thing darkly comical. Why not a horse? Simple. A few blacks could get together and use their horses to sire all the horses they want. Mules are steril. You have a mule until it dies. Then you have nothing. They may as well have given them sacks of AMD seeds that produce edible, but sterile crops.
I believe the Confederate state legislatures passed ordinances of secession, not articles.