The Corwin Amendment passed the House by the necessary 2/3 on Feb. 28 and the Senate on March 2.
Shortly thereafter, of course, it became moot when the CSA attacked the USA.
The only real effect of the Corwin Amendment would have been to change the ratification for an amendment to ban slavery from states from 75% of the states to 100%. And of course if every state was opposed to slavery the institution would already be dead.
It is an imponderable whether a succeeding amendment could have just repealed the Corwin Amendment as the 23rd repealed the 18th. At present there is only one theoretically unamendable section of the Constitution, “no state, without its consent, shall be deprived of its equal suffrage in the Senate.”
Again, it’s an interesting question whether this section could be constitutionally repealed. IMO it could be.
However, since there is effectively zero sentiment to do so, the point is moot.
So, does this Corwin Amendment make the case that the war was not over slavery, and there a hidden motive to send all the slaves South and it didn’t work out?
How they could even offer such an amendment is beyond me.