No mention of the PICs negligence in leaving the flight deck prior to entering an area of severe CB activity. He had to have known that there was severe CBs in the area was there from his briefing and from listening to other aircraft deviating. Any flight over the ICTZ has a great chance of experiencing monstous CBs!
The fact that the relief pilot and the SIC made attempts to call him back to the flight deck signifies that they were overwhelmed with what they faced.
In hindsight, a 200+ mile deviation left or right of the CBs that night would have saved all the lives on that plane. As to why they didn't do this is anyone's guess.