Quite a few BigCos had a genuine job-for-life culture until the 70s recessions hit. A few managed to keep it going until the 80s.

The big cultural change happened in the early 80s as MBA culture became the norm, with a shift towards zero sum neoliberal extremism and the uncoupling of pay from productivity.

We can thank Milton Friedman and Jack Welsh for much of that shift.

Friedman popularized an idea that shareholders should be prioritized above all else and Jack Welsh implemented it at GE, showing just how much profit can be made when you care only about the money/stock.

The information is not new but then there's actually internalizing that information and changing your views.