the 3000 number for maria comes from taking the total death rate in puerto rico in the 6(?) months following the hurricane and subtracting the average death rate for that period in previous years. it's an nonstandard way of calculating disaster fatalities, chosen specifically because it gives a big number that is useful for relief lobbying purposes (it's like 9/11!), and if you calculated 9/11 casualties the same way you would surely come up with a significantly higher number. the number of people killed directly by the hurricane, during the course of the hurricane, was under 100.