> It was the automakers’ failure to compete with highly capable foreign competition.

I contend it was when Dodge won the court case deciding that shareholders were more important than employees. It’s been a slow burn ever since.

> It was the automakers’ failure to compete with highly capable foreign competition.

A lot of their capability was due to them being better at automation. See: NUMMI

Detroit's decline started as soon as assembly plants went one-story in the 40's-50's. There was further decline with the advent of robotics/computers in the 70's-80's, and 2000's with globalization.