......I shall ascribe a significant portion of the “cause” to the aircraft design.
Gums didn't say that aircraft design was the
only cause of this accident. What he didn't say is that several other factors will be found;
1. Pilot training factors
2. Supervisory factors
3. Maintenance factors
...and possibly more.
In addition to considering aircraft design, no accident investigation is complete without at least considering the above. I believe that, at least, the first two have some bearing on what happened.