1. The universe simply does not permit an arrangement of humans that isn't a hierarchy of exploitation and suffering.
2. There is a "natural" hierarchy which is also a just one, where good people deserve to exploit and bad people deserve to suffer, and of course I'm not one of the bad people. ("Just-world fallacy.")
3. Anyone who says don't need to build a Torment Nexus for anyone is a sneaky liar trying to trick their way upwards into a layer in the hierarchy they don't "deserve."
So it's not as simple as sadism or greed, they'll tolerate some being stepped-on as long as they've been convinced that the "right people" doing the stepping and the bad people are getting stepped on more.
A relevant free ebook from 2006: https://theauthoritarians.org
They are also a honeypot begging to be exploited by bad actors for whom life is a zero-sum game. Once a critical mass of those asshats show up, all of the trust that led to the greater efficiency and productivity breaks down.
Greater trust between good actors is efficient but opens the door to free riders. Lower trust is inefficient but handles bad actors. I think basically all of human history is a meandering line around this unstable equilibrium of trust.