There was a significant economic component to the WBTS in addition to slavery (and slavery was wrapped up in the economics as well). Lincoln—a man who was not exactly as enlightened in his opinions about blacks as his hagiographers have made him out to be—was very shrewd in issuing the Emancipation Proclamation and pushing the issue of slavery back to the forefront. Abe wasn’t the secular saint he’s been turned into since 1865, but he was a very smart man and a very sharp politician, whatever else those of us down here in Dixie may think about him.
With a strong basis in the sovereignty of states, the South discovered that a Confederacy, i.e., confederated sovereign states, are at their least efficient in fighting a national war. The strong Federal Union was ironically made stronger by the Confederate defection, starting a trend away from states' rights and toward an ever more powerful central government.
When the main stated reason for the War quickly switched from "Preserving the Union," to "Freeing the Slaves," the issue of states' rights got lost along the way. Unanswered: Does a sovereign state have the right to leave the Union?