Historically, the southern states voted to secede, began raising an army and fired on Ft. Sumpter. Up until that point the union/Lincoln had not freed any slaves, abolished slavery or even proposed to abolish it or fired a shot to begin any hostilities and in fact sought to avoid hostilities. The hostile southern democrats, like democrats today, believed they could do what they damned well pleased without talking to republicans. The south fired the first shots in an effort to keep slavery as their “peculiar” institution.
None of which changes the fact that economically slavery was failing and was on the decline.
Peculiar to them unless you count: Delaware, Kentucky, Maryland, Missouri, and West Virginia the slave states who did not secede and where it was legal until the 13th amendment was ratified about four months before the end of the war!!!!