It's not the only way. The oppressed do not need to become the oppressor, its just the simplest rut for the wheel to turn in.

Sure, they can stay the oppressed?

Using the entropic model you seem to indicate (which I also favor), us vs them seems to be the lowest energy state.

It’s certainly possible to not be there at any given time, but seems to require a specific and somewhat unique set of circumstances, which are not the most energetically stable.