Where "product manager" really started going off the rails was when enterprise agile achieved hockey stick level popularity as all of a sudden the "product owner" role wound up being in the "product manager" job family.
All of a sudden you had "product managers" inserted deep in the bowels of large systems, instead of focusing on big picture topics.
All of a sudden you had "product managers" inserted deep in the bowels of large systems, instead of focusing on big picture topics.