I would have thought that notwithstanding the legalities or otherwise of the flight, it would be significant if the wreckage showed, for example, an engine failure? Hence a very worthwhile investigation. It is of course also possible they may find that the pilot suffered an incapacitation at the controls. I think given the prominence of this case, the emergence of facts would be helpful to quell some of the more absurd hypotheses.
So long as the correct approach is taken to cross water flights in SEP aircraft, the safety record remains very safe indeed and it's vital that we learn causes of any accident. It's pretty clear that the biggest single factor in crashes whether in cars or aircraft remains pilot error, but engine failures at night over water are unlikely to end well where they were at that time.... so if the engine is in tact.... the attribution would lie elsewhere.