Rotorspeed
I guess none of us will ever really know, but there is a disturbing trend in accidents like this where pilots tend to get on 'the pink line' on the GPS and stay on it. That may be why the AAIB elected to mention it, they can't know what he was thinking but he was tending towards the line on the GPS which took him to where the accident happened.
I am sure the phrase has been coined before but I am doing some research into what I term 'The Dangers of Direct To' and will make the results publicly available when I have something concrete.
Several people have known to six decimal places where they died in the last few years, when there was absolutely no need for them (or their passengers) to do so.
GS