It seems that the crux of this case was to do with 'cognitive impairment' and whether or not the pilot had suffered this during the course of the manoeuvre. This was actually one of the main points of the judges summing up.
We can take it then that the defence witness on this matter was either more convincing than the prosecution one, or that the defence team managed to instill enough reasonable doubt to prevent a conviction. So well done to the defence brief for playing the only card he had very well indeed.
Ironically, the actual flight profile flown on the day, and the errors in it highlighted by the AAIB report was almost incidental to the outcome. Strange indeed.