I am fairly familiar with Hyde Park real estate. That house is not in a great location according to my realtor friend. Besides, a $1.25 million house hardly qualifies as a mansion even in Hyde Park. I know people living in 12,000 sq. ft. mansion in Kenwood. Yet even at that size it still will be dwarfed by the Gates 30,000 sq. ft. mansion in Medina. If Ken Griffin can spend $59 million to buy a 4 floor Gold Coast condo, Gates with net worth of 10 times of Griffin can easily buy similar property in downtown.
Here is my speculation. I think Bill and Melinda basically buy this place for Rory so that if he wants to host a party for his friends, they can all go together to a place near his dorm. This house is only 3 minute walk from Campus North.