From what I understand, the constant wars and political corruption of the Roman Republic allowed Roman agribusinessmen to crush the native Roman free peasant class—herding them into large cities while the remainder were forced to be essentially sharecroppers, while the “optimates” bought up their foreclosed farmsteads and built large latifundia worked by slaves in their place.

Since this was due to the ability of Roman planters (which is essentially what they were) to exploit the economy of scale of their plantations (relative to small subsistence farms)—how come a similar phenomenon did not occur under feudalism in mediaeval Western Europe?

(Yes I’m aware “feudalism” is a construct, but we need a way of saying “the social institutions of Kamakura Japan, the Western Zhou Dynasty, the last few centuries of Byzantium, Russia until 1861 and Western Europe during the Middle Ages were all similar in important ways, despite differences” without having to write that long sentence every single time)