I grew up in the city of Detroit. Born 1965. The decline happened in real time all around me while growing up.
It was embraced by the DNC locally as a long term "march" for the "movement." Think "Focus Hope."
They knew their policies were ruinous, but were sold to the unwashed as payback for years of suffering, with a guarantee that - as soon as whitey was done paying and hurting, we would have a Chocolate city of our own that could be transformed into a literal WORKERS PARADISE.
Problem was, the looters never planned to do anything but demagogue and pillage, then get out with their pockets full to parts unknown.