Sounds evil, which it was, but at the same time it was a matter of survival, as proven after the war when many plantations and businesses using the former slaves collapsed.

Yes, but not because they became enslaved to northern machinery. Because the slaves left, having been treated horribly, and the post-war planter aristocracy was incapable of luring any but the most desperate back since the aristocracy was darkly hilariously (in the sense of “the sheer gall of asking someone to come back and work for peanuts or goodwill after enslaving them”) and gruesomely unwilling to pay their former slaves a fair wage, even as their plantations were overgrown and their properties rotted, unmaintained.

Turns out that when almost half of your labor force up and leaves because you’ve been a piece of shit, and you’re unwilling to stop being a piece of shit even to lure them back, the economy slumps. Who’d’ve thought?

The materialist analysis is really lacking on the Civil War. It really was a war of ideas. People, including demographics on a large-scale, do not always act rationally, but according to the values set by their societies.