I donno. Seems like a maintenance nightmare made easier only when you got a cenobium living on the grounds.
Since there aren't enough monks, the church would have to pay people to come in and maintain the place - but they can't really afford that. So, either they let these beautiful places crumble and decay, or they sell them to someone who will hopefully be able to take care of it. Between the two, the latter seems like the least bad option to me. I certainly wish that these places could stay as part of the church and not be some billionaire's home, but I would rather they be a billionaire's home than go to ruin.
or being a billionaire.