Actually, the start of the demise of Detroit started with Nixon in 71 when he floated the value of the dollar. Now, the mere fact that cars are better, last longer, need less maintenance, and are being made more and more by robots has not done Detroit any favors.
Good article in Forbes today about this very subject :
The problem with that argument is that Detroit's demise preceded 1970 as the graph shows population decline started two decades before 1970. As I've shown in a number of cities, the common thread of a city's decline is Democrat rule over decades. Not, its Nixon's fault.