Those with power used that power to strengthen their economic and political positions, or at the very least to maintain them. They also attempted to shape thinking, to make acceptable differences in income that would otherwise be odious.
As the notion of divine right became rejected in the early nation-states, those with power sought other bases for defending their positions. With the Renaissance and the Enlightenment, which emphasized the dignity of the individual, and with the Industrial Revolution, which led to the emergence of a vast urban underclass, it became imperative to find new justifications for inequality, especially as critics of the system, like Marx, talked about exploitation.
The theory that came to dominate, beginning in the second half of the nineteenth century—and still does—was called “marginal productivity theory”…
Joseph E. Stiglitz „Nobel Laureate Economist Says American Inequality Didn’t Just Happen. It Was Created”