> Detroit is a city which was designed from the ground up to discourage public transport
This is simply not true. See [1][2][3][4][5] for the evolution of the transit system, from horse-drawn streetcars onward; notice that in the beginning the city's area was much smaller, but as annexations followed, so did transit.
Detroit's (current) transit woes are ultimately not that different from those of other American cities: transit needs to go where people work and live, and as both of those have become more distributed, fewer areas are suitable. It's really no surprise that this new development is along the highest-density core; it's also undeniable that this is the area that's experiencing a renaissance and an influx of investment. I'd say that these attributes are inter-related, in that they mutually enable each other.