Quite right, this process has been happening since the early 1970s or earlier (if you want to count the capture of the industrial base by unions).
The decline of the industrial centers has been happening for a long time. Creeping socialism is a long process. Technology and the buildout of the Interstate system has facilitated the decentralization of industry.
Detroit was the center of the Car Industry and the Car industry was the first to take the hit of the opening of the US markets to international competition thanks to James Earl Carter, the Destroyer.
Herein northeastern NJ the problem was that the loss of industry removed the principal taxpayers for all of the “services” - and homeowners quickly found themselves on the hook for everything.
My town had manufacturing decades ago, so we had paid firefighters (most of NJ - and the country - doesn’t); they were paid for by industry because industry was the primary reason they were necessary. The industries died or left, but this legacy continues - we pay over a hundred firemen primarily to sleep all day (there aren’t enough fires to even justify the cost). The union opposes regionalization (there are several small, densely populated municipalities that could certainly share services like this), but it doesn’t happen enough - so the taxes are far higher than in other areas (for dwindling returns).
It has only chased out more employers, which chases out employees - so we end up just being a dumping ground for an increasingly-illegal immigrant population. We’ve replaced the previous economy with a hybrid of government employee caste/poverty industries (and there is little private-sector middle class, and no upper class, in more and more areas).