There was an incredible amount of great culture, neighborhoods and businesses destroyed by

1. intentional running of highways through tight-knit ethnic neighborhoods (everybody - Polish, black, Etc) running roughshod over private property and eviscerating the areas.
2. “burn baby burn” - race riots
3. some underlying racial tension built in (a la Henry Ford).
4. National rapid moral decline, drugs, insanely corrupt Democrat city political machine

My mom describes how her and friends used to travel to Detroit for the day, and it was beautiful - all the architecture and tall graceful elm trees lining the streets, ethnic groups got along and mingled socially and in shopping and entertainment, (at least in her age set) — and how it all was obliterated in the late 60’s.