Slavery was definitely a large part of that. And I think this is both something that southern apologists need to start understanding and those who criticize the south also need to start evaluating in context.
Take into account that for the south at the time slavery WAS the economy. The south wasn't industrialized like the north and wouldn't be until railways managed to fix their serious communication issues, so slave plantations were almost all of their actual resources, and they were extremely valuable precisely because of slave use. Without slavery, their revenue streams would get assreamed hard and the overpopulation would set in fast. Now you may think "what overpopulation lol their density was shit" but take into account that back then we didn't have nearly the kind of irrigation systems we have now, nor the bleeping trains to communicate cities. Yes, there was a lot of land, but it was a lot of completely uninhabitable desert wasteland, when you take into account the need for HABITABLE land which has FOOD in it, oh the south had a serious issue if slavery was abolished just like that. Between the loss of money culling exports (and therefore also imports) and the need to turn plantations into farms to account for the loss of those imports leading to even more loss of money, it was a very visible and notorious issue which had already caused genocydal servile insurrections in the caribbean's colonies, something the southerners were very open about being their greatest fear.
Ironically enough the reason this in the end turn out to be far less of an issue that they feared is actually because of the war. Namely because it solved the overpopulation issue by means of... well... culling a whole lot of people. And because after the war the need to recover national pride and unity lead to a hard turn back into the frontier mith to claim the indian territories which also heavily expanded the amount of livable land. So had the south not rebelled, there is a very good chance that the frontier myth initiatives would've been a lot more cucked and there would've been a lot more people to feed, resulting in a very good chance of the feared servile insurrection ending in the persecution of white southerners and a civil war between the freed slaves turned secessionist and the north.
Kind of fucked up when you think about it. That the way shit was built before the war, south didn't really seem to have any chance of avoiding bloodshed, it could only choose between being the ones it's done to, or attempting to be the ones doing it. I'm not gonna blame them for choosing the second really. If anything, I hate lost cause revisionists fare more than the actual civil war southerners, even if I seriously disagree with their political ideas. Can't quite say I got anymosity against someone for choosing the wrong conclussion to a question that had no right answer. But I certainly can muster up vile towards those trying to cover the truth just because it doesn't fit their CURRENT ideology. Your ancestors didn't think like you, they also didn't live in times like the one's you're living in, get over it already.