> belief that slavery was really ended by industrialization making abolition economically advantageous
On the contrary, historians broadly agree that industrialization (particularly the advent of the cotton gin) actually turbocharged the human trafficking industry in the US. The cotton gin moved the bottleneck for textile production onto enslaved people, since there was no automation available for planting, cultivating, or harvesting the cotton.
Not only that, but slavery in the south didn't "end" anywhere near as fast as people think it did. Even when plantations stopped using chains and shooting people for leaving the plantation, they just switched to slightly more subtle ways. Sharecropping, barring them from owning property, running lynch mobs to kill anyone who stepped afoul of the unspoken rules, and not allowing black people into most public spaces.
To this day southern conservatives talk about "state's rights" as being the reason for the civil war. Yeaaaaaah no