It doesn't quite work like that. The South was extremely rural until the second world war. Industry really only started appearing large amounts. The South was dominated by agrarian interests whose cotton and tobacco was sold around the world, making them a hefty fortune. There would be no profit incentive to switch to industry. They had a comparative advantage in the production of cash crops. The Southern leadership was thoroughly pro free trade for through it, there would be cheaper prices for manufactured goods for the Southrons to purchase due to proper competition between American and European industrial goods, with those American manufactured goods being largely produced in the North. As the Northern United States was one of the premier centers of industry in the world, its ability to efficiently produce manufactured goods would have made its would be southern competitors go bankrupt within the hour. The efficiency that was in the North vs having southern slaves mass produce industrial goods would have been so staggering, it would have been comparing Wallonia to Southern Italy. The transition to industry for the slaveowners would have been costly, unproductive, and a most financially bereft venture. Not only were the productivity levels so much in difference, but the fact that they were part of the same country meant that you couldn't have any tariffs to protect said potential industrial firms in Dixie, and so the venture would have been even more pointless.
Interesting you bring up Marx. Such an idea does fancy a good old fashioned communist, as it is the rapid transition from the agrarian stage to the industrial stage. However, history and economic theories have taught us that such policies are in fact bereft of success when put to the test called reality. No no, it makes perfect sense why the South did not industrialize earlier, and a slave-based approach to it would have been pointless, costly and resulted in complete and utter failure.