Two things killed Detroit.
The July,1967 riot
The demise of the American auto industry.
Oh,and the abysmally bad school system makes it three.
One thing killed Detroit - Coleman Young!
The effect of the riots could have been mitigated with a mayor who was not a communist race baiter. As for the auto industry, it has affected all of Michigan, but the suburbs are doing great with good schools, all services and very good housing.
Today, there are only 3 reasons to even go to Detroit. They are the Detroit Tigers, Red Wings and Lions and the Lions aren't much of a reason.