Regulation, wages, and unions did not scare away businesses. Detroit did not/does not have a very diversified industry because it does not have a population with diverse skills. In fact, most of the adults are frankly un-hireable outside of manufacturing, food service, and very basic hospitality services.
Half of their population is functionally illiterate and they have a
75% high school dropout rate. Detroit’s problems are the result of one reason and one reason only; a citizenry which places almost no value on education because they could always just go work at the factory like their father and his father and his father before him. Now the factories are gone and they’re left with no education, no skills, and no jobs.