It was not a simple engine failure followed by a ditching. Either the aircraft stalled or control was not maintained and the aircraft impacted the water at high speed. Generally in a accident like this there is a distraction that causes the loss of control. Could be a engine failure, rough running engine, cargo shift, instrument failure ect.. The Golden rule of flying is prioritize aviating, navigating and communicating in that order. The next rule is if a accident is not avoidable fly the aircraft all the way to the crash. You might walk away however if you stall or lose control the outcome is never pretty.
Someone mentioned fuel. One of the big issues in the Caribbean is water getting into the fuel. A slug of water will stop the engine. Water can get in the tanks through condensation, bad fuel caps or poor practices by the fueler. Aircraft tanks are supposed to be sumped for water before flight but crashes caused by water occur often.