>Slavery was more stable: lasted millenia.

And slavery required less violence, per capita, to maintain? I don't think so. Innumerable slave revolts. Wars of conquest to capture slaves. Slave raiding. The daily violence needed to enforce slavery. Sexual violence perpetrated on slaves.

Capitalism is a rock of stability, from a civil society perspective, in contrast. When was the last time a developed capitalist nation had a civil war, or even a major violent revolt?