When did we decide that someone who spends all their day doing hard physical labour will get paid wayyy less than

Supervision is a professional skill. A good supervisor is worth their pay. An incorrectly paid supervisor is never a lasting employee. Too much pay, the boss will realize the incompetence and replace him. Too little and the supervisor will seek a better check somewhere else.

Supervisory roles vary, and some are high demands and stress. Planning and execution of the daily workflow and designation of labor with the ability for contingency restructuring through the days shift overlaps.

Capitalism vs Socialism.

The companies know nobody really wants to do these jobs, and they don't require years of expensive education, so they know that those who sign up for them are doing it out of necessity/desperation (in order to not go homeless). So the companies can pay them dirt because they know the workers don't have much choice.

Yes. Welcome to the system

Since around 1790 it's the same.

It's always been that way. How many real jobs have you had ?