The "South' didn't exist. Neither did the 'North.' These are both shorthands for vague and amorphous coalitions of millions of people and thousands of decisionmakers and influencers of various kinds with shifting and often conflicting internal ideas. The way these coalitions settle on an issue is often quite contingent.The South doesn’t want the Corwin amendment. They nothing less than slavery to be fully legal in all states and territories. Forever. Not just no federal interference, no ability for anyone to ban it.