I believe the reports said that there were no rental cars available. This makes sense - cars being available depend on cars being returned. If you had a car, would you return it? I've been in 'normal' situations when stranded overnight at an airport, and cars run out quickly. And, flights fill up quickly as well. I traveled for 8 years or so - you really have no idea how everything is 'just in time' in the travel industry.
Also the rent-a-car people simply evacuated, there was nobody to rent the cars.