The following comment is generic about accident and incident discussions I have observed over the years and may or may not pertain to this incident.
Nearly half of all scuba fatalities begin with a medical event, such as a cardiac arrest. When that happens, there is usually no clear sign of what happened. Unless the diver's buddy happened to be looking right at the event when it happened, it will not be witnessed--the diver will suddenly begin sinking, often disappearing from view, and be found after a frantic search. There is often no autopsy, but when there is, the results are rarely released. It is private information for the family.
But in the world of accident and incident discussions, people insistently believe there must have been a preventable cause, and they search for it. They look for every possible clue of what the diver did wrong, or what the buddy did wrong. They keep waiting for more information. They keep demanding more information. But more information will never come.
In one thread a few years ago the information that the diver had died of a cardiac event of some kind was indeed released, and several people still insisted something must have gone wrong on the dive. Heart attacks don't happen without some triggering event, they said. Well, the truth is that people have cardiac events without triggering events all the time. The second most common time to have one is when you are asleep. The most common time is after breakfast.