I don’t know how to put it simpler than this:
FDR and his progressive Democratic Congress passed tax laws so corporate profits would have to be split with the employees of a corporation.
Reagan and his Republican and neo-liberal Democratic Congress passed tax laws so CEOs and stockholders could walk away with all the profits and so the incentive was to pay American workers as little as possible.
This is why and how America lost its middle class over the last 40 years.