They would continue to rent somewhere else, such as purpose built rentals, rentals where the owner is also a resident, or they could themselves buy housing that isn't being hoarded by the rich.
They are making passive income with this house, not working their arses off. They are not doing this to be altruistic, they are doing so to profit off people's need for housing.
They make it clear it is an investment property, and not their primary residence. I similarly don't feel bad for people who lose money in the stock market when investing beyond their capabilities. They sold a house as vacant without any guarantee of that being true, it's 100% on them to eat the loss IMO.