The problem is that we might never know what happened unless the aircraft is located and examined. It could have been a mechanical engine or airframe failure, fuel contamination, a fire, or pilot error. Those who are quick to blame the pilot are simply speculating. We should wait to hear what the NTSB comes up with. Even then, without the aircraft to examine its conclusion will be, in part, speculation. And Lake Clark does not give up  airplanes that crash  in such deep water very easily.