I worked in real estate asset management for twenty-five years. There are a lot of factors at play in the decision to sell a property. We do not have most of the information the WTBS would have used in making a decision to sell and leave, therefore anything we think of the decision is pure speculation. There does come a time in the life of a building when selling it makes the most sense.
There are numerous problems with the scenarios outlined above. Those are old buildings and getting them up to code and rebuilding the core systems would have taken a huge amount of cash. A new owner can take advantage of the tax code to make that worthwhile. The WTBS can't make use of those advantages. Also, they can't use volunteer labor to rebuild them for commercial purposes or to maintain them after they are put back in service.
As I said, the only thing we know is that it looked like a good plan to them. I think there are good reasons to think they may have been right.