This was always coming. Slavery was going to go away no matter what. The real issue that caused the civil war has still not gone away (The NorthEast runs the nation for mostly it's own benefit) and is still with us today.
Nowadays we call it the "Swamp", or the "Deep State".
DiogenesLamp: "This was always coming.
Slavery was going to go away no matter what."
More nonsense, since slaves in 1860 represented the biggest single asset value of the United States -- estimated at $4 billion total in an economy with a $4.4 billion GDP.
There was no possible way that slaveholders willing to declare secession and war to defend slavery were suddenly going to throw up their hands saying, "oh, never mind, slavery is not THAT important after all!".
So, what about 25 or 50 or 100 years in the future?
Well... can slaves run machines, work in factories, help maintain & repair equipment?
Of course they could, now support slavery with a powerful & aggressive Confederate military, expanding into the Caribbean, Central and South America, and what exactly would stop slavery?
Finally, suppose in WWII the world's slave-powers allied and defeated western social democracies, including FDR's New Deal USA, now what would ever prevent slavery's ultimate victory??
Nothing I can see.