There's lots to discuss here, so not discouraging other respondents, but meawhile you may be interested in some earlier posts on Detroit specifically, and the broader topics of deurbanization and "white flight":

• What led Detroit to the state it is in today? <-- includes links to loads more posts -- check them out!

• Is this Redditor's "Best-Of" comment about the history of Detroit accurate?

These posts have all been archived by now, so if you have followup questions for any of the users, just ask them here & mention their username to notify them

The decline of Detroit was brought down a variety of factors that comfined into the perfect economic storm. As this New York Times article describes from Thomas Sugrue's Motor City essay, alot of credit goes to lack ofd iversity and decentralization. The city was very much reliant on one industry: the automobile industry. A shift in change of employment would mean a huge shock to the economic since there would be no "fallback". also the employment of a huge amount of workers meant it would be extremely vulnerable to be targeted by unions such as the UAW.

What really brought it down was the fact that a combination of lack of diversity, unionization and a shift in the economy weakened the construction, leading to the Detroit Three to seek elsewhere for construction.