Why did the South use slavery in their economy?
The South was doubling down on slavery at the same time the rest of the world was abolishing it.
The antebellum South didn’t invent slavery. Prior to the 19th Century, it was practiced in some form in much of the Western world, including the northern states when they were colonies. It was even mentioned in the Bible in a way that didn’t condemn the practice. It was so commonplace that most people didn’t really think of it as evil or wrong.
It was in this slavery-friendly environment that the South, already invested in the marginally-profitable crop of cotton, entered the industrial revolution. The invention of the cotton gin made cotton profitable. And the planters who bought more cotton gins and more slaves became insanely profitable!
The parts of the country (and world) that were making money without slave labor rallied around abolition of it. Southern planters who had already invested their new fortunes into more slaves were not swayed by the rest of the world’s newfound conscience on this matter, and nothing short of losing a war changed their minds.