As I see it....the Sixty-Four Dollar Question will always be...."From the time the crew observed the MGB Oil Pressure below 5PSI....why did they not make a timely descent and ditching?"
That is not going to be an easy question to answer as they are not here to tell us. The CVR will have most of the answer. I suspect the conversations between Dispatch/Ops and the crew will also bear directly upon that decision.
Hind sight being perfect....they should have ditched the aircraft much sooner than they did. We all know that because of what happened. They did not have the benefit of that knowledge in advance....and did what they thought best at the time.
Why they did what they did is the heart of this investigation. Let's hope the truth comes out...whatever it is.