You touched on one of the two major problems that caused this change: Reaganomics and money in politics. They are of course related. Giving corporations the right to bribe - I mean contribute to - politicians and Reagan's war on labor has moved the balance of power over the last 40 years significantly towards management.

Strong unions help everyone, not just blue collar workers. Everyone "above" blue collar also benefits. Outside the US unions are also for white collar jobs.

Management feels empowered to treat workers like shit because the balance of power between management and workers has been lost in the US. It will not get better until balance is restored.