[cardanome]

Slavery in the US made sense for a limited time but at some point it would have hold the US back economically. It would have lacked enough free workforce for the industrialization and so would have fallen vastly behind compared to other countries.

Slavery is very profitable for the slave holder but not for the society as a whole.

Like if you take Nazi Germany. Many companies got rich by being provided essentially free slave labor that they could free work to death. But does it really make sense to have educated people work themselves to an early grave doing menial inefficient labor that needed to be closely supervised? Could they not have provided much more to the economy if they had been free? The practice is as sustainable as eating your own flesh.

Nazi Germany could keep going as long as the war machine kept going and there were countries to occupy but it wouldn't have been a very sustainable society in the long run.

Yes capitalist have an individual interest in slave labor and in forming monopolies. But in doing so they also also create conditions for the undoing of the very society that made them rich. That is exactly the point. Slavery is amazing for the slave owner but not for everyone else.