The incident involved an aircraft that crashed outside the airfield boundary and outside the display area. The AAIB report has eliminated the possibility of any major fault in the aircraft as being responsible for the crash. Some pedants might argue otherwise, but essentially the aircraft was airworthy. That places the blame firmly upon the pilot. That will inevitably have to be the finding of the inquest and any further proceedings will carry on from there.
Various shortcomings have been discovered during the course of the AAIB investigation concerning safety procedures, but even if these had all been ccorrectly followed, it would not have altered the outcome of this specific incident. The organisers of a display have a responsibilty to try and ensure the safety of spectators at the display. They cannot be expected to take responsibility for unforseeable events that take place outside the display area.