I recommend visiting Detroit to update your priors. I first visited in 2000 and it was blighted. I visited again in 2025 and it’s actually nice (downtown Detroit and surroundings). There’s even a Microsoft office there.
> One surprising thing is how quickly it got blighted.
I don't think this is actually true - either that it happened quickly, or that how quickly it happened was a surprise. Detroit (the city, which was always the "problem") depopulated from the 1950s onwards as the major industry moved to the suburbs, and the effects were obvious even in the 1960s. It took another 40-50 years to hit the bottom though.
That said, the population is now growing again (since 2021).