> Once people were not as blinded by profits, they could actually see that slavery was a moral evil.
It was actually quite the opposite. Pre-industrialization, serfdom and slavery were basically equivalent. You hand a local lord and if you worked for him you got food and shelter. Your alternative was to run off into the wilderness and fend for yourself, which frequently meant starving or freezing to death or being mauled by a bear. Unsurprisingly not many people chose that.
Then factories show up and suddenly your alternative is to run off and go work in the factory. Naturally many people started preferring to do that, which turned the plantations upside down because their economic system was based on the workers not having anywhere else to go.
Their response was brutal. Chains to keep slaves from running away, hunting runaway slaves with dogs, savage beatings, etc. None of that stuff was really commonplace before industrialization. The response to industrialization was what made 19th century slavery so much worse than traditional serfdom.
But that response was as futile as it was brutish. The factories made slavery uneconomical. You can't defeat supply and demand with chains and whips. All they do is cause the slaves to want to run away more.
The factories destroyed slavery directly, by out-competing it. It's questionable whether the war was even net positive -- that was a whole lot of blood spilled over an economic system that couldn't have sustained itself much longer in any event.