https://whydontweownthis.com/2014/mi/wayne/detroit#15/42.347...
6000 homes spread out also means you can also create a mini company town by essentially luring people (for a new company) to the city and giving them a choice of different properties, renovated and ready to go with efficiencies gained by having so many to deal with. (Similar to when, say, Levittown was built (all in one area of course but same concept with construction).
I'm not a city planner and am not very well versed in municipal zoning laws in Detroit so I wonder if its even a possibility.
My guess is that this is speculative property investment, likely as part of a private REIT/hedge fund. I bet the buyers plan to turn around and sell these off in small lots (usually 10 - 100 at a time) for a small profit.