A bunch of landlords all use the same software to tell them how to price rents. The software continually pushes prices higher and higher. The software requires landlords to use their pricing as a condition of use. Now you have a price-fixing cartel for rent.

And those corporations can decide that they'd rather the apartment sit vacant than be rented at below exactly what they'd like to get for it, bolstered in part by the fact they can claim the non-occupancy as a loss on their taxes.