I know Prater was after the building to do residential once ProMedica had walked away from it and their idea of a med/tech incubator space, but don't know any details about why U-Haul was chosen. Could have just been a higher offer.
The Warehouse District pushed U-Haul to look at other locations around downtown, maybe something less "in the middle" of everything, something more industrial--friendly, etc. With the pace of progress in terms of residential development lately, the thought was that keeping this building available for a developer would be the highest and best use, but ultimately, it's another free market issue.
There have been a number of protests from area residents who are not excited about the possibility of those bright interior lights shining all night long. I can only imagine what the residents with windows across the street in the Bartley will be thinking. The Warehouse District can restrict lighting and signage on the exterior, but there's very little authority over what someone can have on the inside. Just drive down I-75 at night to see how bright an interior light can be.