I read somewhere that this happened during the Great Depression as well. A large number of homes sat vacant or were rented out by the banks, since selling them would realize massive losses. In many cases banks became long-term landlords until real estate recovered.
My bet is they do the same this time around. There’s no reason for them to rush to dump their shadow inventory on the market, decimating prices and incurring losses. Better to hold out. Just like individual “accidental landlords” – plus banks have the advantages of much larger staffs and balance sheets to weather the storm. Government backing is the icing on the cake.