What happens is that economics shift from a renewable model to an extractive model.

Farms are renewable so farmers maintain them over centuries. Mines are extractive so they get pumped and dumped.

What landlords do in these situations is try to extract as much money as possible before the enterprise collapses, either literally or figuratively. New housing doesn't come online quickly so both quality and quantity fall.

Well, this is a reason that we have standards and laws about rentable properties.

Landlords who can’t operate within the imposed constraints, those for instance who have debts they used to get into the game in the first place, might simply be forced to leave the business.

In many markets this is actively desirable.