By the time the Corwin Amendment passed congress, 7 states had already announced themselves to be a different country. They couldn't even consider the amendment without admitting that they were, in fact, still part of the United States and that secession had been a charade, something southern pride would not accept. It was a Catch-22 in that sense.
Always left out of these discussions is the fact that these two cities were collecting *MOST* of the money produced by the South.
Same two f***ing cities that are still trying to control the rest of us today.
If slavery and protection thereof had been the big issue to them, slavery by express constitutional amendment would have addressed those concerns.
Lets run through the math again.
15 slaveholding states at the time. 3/4s of all states required to pass a constitutional amendment. Ergo, to abolish slavery at some future date, it would take 45 states voting to pass that future amendment over the objections of the 15 slaveholding states. 45 + 15 = 60. How many states are in the US currently? The answer is of course 50. Ie not even close to enough.
Slavery would have been irrevocable without the approval of the slaveholding states. They could do basic math back then too. They all understand it would have meant slavery effectively forever. Yet the original 7 seceding states turned it down. If it was all about slavery why would they?