Detroit failed because of automation and off-shoring.
That’s the mechanism behind why it failed, but not the reason for the policy. Automation and off-shoring were tools intended to re-segregate and depress the wealth of the working class. Once the city sufficiently shocked into collapse, financial investment came flooding back into the city in the form of foreclosure sale purchases and low-wage service sector expansion. The modern city is seeing the first population expansion it’s enjoyed in decades, but with an enormous new disparity in income and political organization between the richest and poorest residents. Dan Gilbert, the co-founder of the largest private mortgage lender in the US - Quicken Loans (now Rocket Mortgage) - owns enormous swaths of the downtown district and has his talons in a host of municipal and state political figures.
He’s revitalized the city with enormous amounts of public money, laundered into private profits, through the private lending racket. And he’s used the depressed wages and real estate values in the town to reap huge margins on the cost of labor, relative to more traditional finance centers like New York or Dallas.