"wasn't able" is dubious. Of course, there are repercussions for not moving out on the date, but it's not an imperative. If the landlord had to move his stuff to the curb, or it delayed closing on a house, that causes a cascade into another transaction. The world doesn't stop, of course. If the landlord is forced to pay movers to put your stuff in storage and send the bill to the tenant, those costs can, in theory, be passed on to the moving company. The details depend on the contract, obviously.