I have read sources from across the board for fifty years including those beloved by the Defenders of Slaverocracy.
There is nothing important that hasn't been amply handled.
The Rebellion was started by men who had worked throughout the 1850s to destroy the Union and protect slavery. There is no doubt about this. Nor is there any doubt that they would do ANYTHING to protect slavery and that included expansion into the Caribbean, Mexico and Latin America. Fortunately for the world America had a leader who put a stop to their insane plans.
Slavery was an economic impediment to the non-slave South but that didn't matter since power was held by the Slavers and THEY profitted. What did it matter to them if it impoverished the entire region? They cared only about ONE thing, slavery.
Well, slavery WAS legal. And moral or not, men who owned slaves had a huge economic investment for not ending it. The bottom line is that slavery or not, states-rights dictated the right of the states to decide the issue, NOT Abe Lincoln, and a Republican Congress.