Hebog
The AAIB report is a distilled compilation of many reports from many authors, with information from multiple sources, that is why there are apparent discrepancies in different parts of the report when taken in isolation.
The general gist of the report is that there were no major faults with the aircraft that could have caused the accident, the aircraft appeared to respond as expected to control inputs that were directly visible inside and outside the aircraft, and that the subsequent crash was down to a failure to initiate a recovery manoeuvre coming off the top of the final loop.
Naturally the AAIB do not put it as bluntly as that because it is neither their job nor responsibility to assign blame, merely to establish the circumstances that gave rise to the crash in the interest of preventing another similar incident.
While we may have every sympathy with the victims of this incident, including the pilot, who was also equally a victim, only one of the victims can be considered to carry sole responsibility for what happened.
There will be extensive legal arguments over the precise sequence of events and where blame might lie, but from the details already published there is only one reasonable conclusion that can be drawn, pilot error.