I'd blame Winter Music Conference and the constant stream of other huge party events as much as anything.
These people have been enabled by dirt cheap Airbnb prices. Traditional hotels have higher prices but also enforce codes of behavior that tend to limit if not outright ban the incidents I described. Simply, you can't get away with behaving like that in a hotel. You have to keep up appearances. Even in a party town like Miami Beach. Not to mention there's competition for the rooms with regular tourists. Airbnb allows a gang of 20 ppl to rent a single room and come here to wreak havoc.
Also, look at sites such as Hotel Tonight. Personally seen < 50 a night rooms.
The hotel industry distortion field is probably stronger in Miami Beach than almost anywhere because so much money depends on it.
I also don't believe that most the Airbnb rentals on Miami Beach are particularly cheap. The one nearby that I know of charges many thousands per night as its a mansion.