The fact is they are generally owned by the City, having been confiscated for non-payment of taxes.
Essentially, Detroit's economy is now non-existent. The only employers remaining are governmental -- meaning they consume tax money. There are no meaningful non-government employers -- meaning there is nobody left to pay the taxes that the government consumes.
That’s the classic death spiral. Put the taxpaying entities out of business and then the leeches will starve. I have also seen it played out from the regulatory side, which in some way is similar to taxes. The regulators put those they regulated out of business, then who do they have left to regulate? They’ve destroyed themselves by ruining those who justified their existence.