I'm reading How Europe Underdeveloped Africa right now, and Rodney offers that the inherent opportunity for sabotage in more advanced machinery means transitioning beyond a certain stage in development requires "free" workers, that slaves require high degrees of surveillance and are limited to using tools that are hard to destroy.
This is a convincing argument to me for why a transition away from slavery has a material requirement for free workers under capitalism when it comes to factories, but there was still (and is still) a ton of labour that is ultimately performed without advanced machinery, principally agriculture.
I suppose my question is, wouldn't a maximally beneficial set-up for the bourgeoisie have been one in which the cities had free worlers, but the countryside still was allowed slaves to pick oranges etc? (I do know that most agricultural labour has been replaced by complex, easily sabotage-able machinery now, but that was not true in the 19th century)
(and if anyone has any recommended reading on the topic that's appreciated too)
The owner class is always at each others' throats, so don't discount the hypothesis that some owners saw the gain in ending slavery and became more powerful than the other owners (literal slavers).
Look to two things:
What was the impetus to end slavery and, most importantly for ruling class issues, why was the impetus tolerated rather than outlawed and propagandized?
After the American Civil War, which owners gained?
For (1), don't discount the aspect of moral outrage and organization by abolitionists. Marxism emphasizes material conditions, but doesn't discount human agency and our ability to also shape our own direction. The proximal effort was by abolitionists pushing to end the expansion of slave states.
But let's get to material conditions because they are so often underemphasized. So long as abolition was directly opposed to ruling class interests, it would usually get quashed, after all - and ending slavery is clearly against the material interest of slavers. Without revolution or the ability to otherwise depose the ruling class, abolitionists would not be able to accomplish this on their own.
The settler push West was a major driving factor, and also had proximal causes re: the American Civil War. Namely, whether new states - created through genocide and replacement of the Native Americans - would be slave states. This was the tipping point issue of the Civil War, and there arec liberal narratives about it, but it's important to see the aspect of it that is an intra-ruling class fight over who will own land, resources, and production in those new states. And moreover, the slave states' ruling classes saw themselves becoming politically, and then economically dominated if they ever lost the Senate. They relied on a form of regional protectionism to not get bought up and deposed by richer northern businesses, particularly the rapidly growing industrial capitalists. They, probably correctly, saw their own doom when Kansas was admitted as a free state, hence the South starting the Civil War. And the proof is in the pudding: the North did end slavery, but also absolutely did not ensure fair equitable conditions for the formerly enslaved, instead throwing people at the mercy of a racist society and agricultural work that started out pretty similar to slave conditions and slpwly morphed into segregated wage labor that was deeply exploitative and left the vast majority in extreme poverty.
So that's point (1) leading to point (2). The issue was allowed to come to a head, even pushed, aa a fight between ruling class factions. The deeper material conditions are an increasingly powerful capitalist class, including industrial capitalists, that wanted to break open the South for their own exploitation. They also wanted the new states for themselves. Their own ascension was driven by industrialization, the railroads, capitalism, etc etc.
For point 2, just look at where reconstruction went while the north had a monopoly on power. Protectionist policies disappeared, former slaves were made into sharecroppers and wage laborers, and large portions of Appalachia, Virginia, and the Carolinas were bought up by capitalists, turned into extraction efforts to feed industry, and sometimes themselves industrialised. With Lincoln's death this monopoly ended and Southern planters forced themselves back into power, though less than they had before and more regionally restricted to the Deep South, where northern capitalists had less interest. Back in power, they created Jim Crow and terrorized former slaves into apartheid conditions and incredibly exploitative wage labor.
Another common Marxist point at this juncture is that under capitalism, wage laborers' pay tends to get driven down to subsistence (or even below), at least until something gives and the ruling class chuckleheads figure out they get better profits with a minimally educated, housed, and fed workforce. Anyways, a common Marxist refrain is that wage labor of + renting to former slaves was more profitable than slavery, as now subsistence was not the owners' problem. The fact that black people could still be treated and exploited as an underclass suited them very well and there was no way an attempt to restore slavery would have any material base.