Politics no doubt did play a part, but so did the residents themselves, many of whom participated in the 1967 riot that resulted in widespread destruction of property, loss of life and over 7,000 arrests.
The subsequent caving to the black militants--who didn't speak for but a small fraction of the black population--by white liberals trying to "save" Detroit probably intensified racial animosities and contributed to the city's population decline. You had blacks as well as whites wanting to get out while the getting was good, while they could still sell their house, before things got any worse.
I've never had the experience of visiting Detroit although I have friends there. They put me onto a remarkable photo book, The Ruins of Detroit. It has a number of before-and-after images that tell a story no writer could possibly relate.
The book is a little pricey; however, one of the authors has posted images from the book at Amazon for us cheapskates to view.
Truly horrifying. Many parts of Detroit remain just as they were after the 1967 riots; other areas have been leveled with no plans to rebuild.
One would wonder who'd want to live there.
Call it "rural renewal."