To Opherben
As an experienced investigator, then, you should know that not all investigation agencies, including some of the world's most respected, and no researchers into causality of accidents whom I know, think an assignment of "primary cause" is appropriate.
Indeed, all those professional researchers researching failures and accidents causally whom I know consider that most accidents result from a conjunction of many causes.
There are many ways of selecting one cause to "put on a pedestal". My view is that, if one wants to do this, one should explain and justify one's selection criteria in the report.
I know the senior researcher, who has a world-wide reputation, who prepared the human factors report on this accident. I regard the insights in his report as very high quality, and some of those insights made it into the final report.
It will be obvious to you, having admittedly read only what we might call the "Executive Summary", that the investigators were reporting on all the safety issues which they found, not just those which were causally related to the accident.
PBL