The deindustrialization and depopulation really hurt Detroit. But what also strikes me is the rapid change in racial demographics. In 1940, Detroit had a 90% white population and was the highest standard of living city in America. During the course of WWII, 350,000 blacks moved into Detroit. In 1943, the Detroit Race Riot caused by tensions between whites and blacks resulted in 43 dead, 433 wounded. In 1967 it happened again, this time 43 dead, 1189 injured, over 7,200 arrests, and more than 2,000 buildings destroyed. President Lyndon B. Johnson sent in the Army to quell it. In 2010, the demographics are 10% white and 82% black, and Detroit is a bankrupt wasteland.
Deindustrialization happened in other cities such as Pittsburgh - but they've recovered by transitioning into technology/medicine industries and the like. Pittsburgh has not seen a demographic shift like Detroit.
http://en.wikipedia.org/wiki/Demographic_history_of_Detroit