Lots of the modern mid-level bloat came from Job Justification. Can't justify your six figure manager job if you're not managing people. Can't justify making more than the other manager if you don't manage more people than him. Can't justify handing out a promotion if there aren't more people being managed than before.
In more normal times, budgets limited this sort of chicanery. For the past few decades, Wall Street, VCs, and the Fed have been pumping endless free money into big corporations for various unusual and unsustainable reasons. It's starting to unravel now though. Grab some popcorn.