I'm guessing they had to move due to life circumstances, but due to taxes, transaction costs, sunk cost fallacy, hassle, etc, decided not to sell the unit.
Every reluctant landlord capitulates and sells... eventually.
How is that different than a non-reluctant landlord or a capitalist?
It's the same intention: Increase the short term return on capital
Increased return in monetary terms but maybe not quality of life.