Formal Accident Report by the Florida Fish and Wildlife Conservation Commission.

In short the anchor had been tied to the front of the boat (right) but when the anchor got stuck to the seabed they tied it to the rear (wrong) and tried to use engine power to pull the anchor free. That flipped the boat immediately.

In large it appears they were wwwaaayyy over their skill level being out at sea over 50 miles from port in 5'+ seas in a 21' outboard boat.

A SAR beacon would have had them in bed on time. But simpler still, the accident was preventable by checking weather reports, or perhaps realizing that they simply didn't have the experience needed to be where they were.