I believe Wayne's comment is slightly inaccurate in that the vast majority of all rebreather fatalities are associated with FAILURES BY HUMAN OPERATORS better categorized as:
I think what you're getting into here is a higher level of precision than the average diver (much less non-diver) is prepared to fully appreciate the nuance of or speak fluently on.
Before all the facts are presented and the incident can be really teased apart by thorough (or, as-thorough-as-possible) accident analysis I would say it's important that as many people from within the dive community understand and can present as simple a message as possible. I'd agree with Wayne's easy to digest, "the majority of all rebreather fatalities are diver error," for now.
This is not to say that all rebreather divers who die are terrible screw-ups, nor that in this, most recent tragedy, that the divers we lost were terrible divers. By what little I know they were both accomplished, experienced, and capable. So, perhaps the easy lead-in to the more complex message that you raise is that even the best among us are capable of tragic mistakes.