Also, its just attrition.... the Pattersons and Youngs are all dead and buried at this point, along with at least some of the people who populated Oakland County and Detroit during their terms. The suburbs of any city, be it Detroit, Philly, Milwaukee, Chicago, wherever, are now populated much more with people who the grievances of the past don't register. Not totally, but they are different and they are changing...
With respect to Michigan, I really think Donald Trump ****ed up when he came to the Detroit Economic Club and took a big giant dump on the city. And wouldn't be surprised why (though polling is close) that Michigan seems to be drifting toward being Harris' best swing state.
(And perhaps why Debbie Dingell, a person who is never relaxed before an election, was playing beer pong yesteday)