Went and found myself a computer with a much better audio, and for sure one can hear the blades overpitching with Nr running down prior to the sound finishing, almost similar to sound of blades in an auto touchdown.
Regardless as to how good the T/R design is it will lose effectivenss / authority once the Nr winds down too far, that appears to be what happened which can be seen (A/C beginning to rotate) in the video and as Crab says.
The most important factor seems to be stupidity for sure. However it may serve as a good illustration for the adage; Never Descend Downwind, whilst Decreasing Airspeed.
The A/C does not have to enter the magic VRS formula it can simply be placed in the position of not having enough power to arrest the rate of sink set up, and bingo, it damm well falls on the ground and gets all broke up.
The power margin in this case is nowhere near enough to be thought of as enough.
Plenty of blokes have done exactly the same thing in similarly configured '47's or Hillers of identical or more power with far less weight and stuffed up into the ground. 2 - 3 inches spare is bugger all, he could have pulled past the redline (probably did) and it still would have been not enough.
That is one of the problems with Frank's automatic governors, half these dudes don't even know that they have overpitched until the bells start ringing, and then they stuff up.
quite sad, it buggered his whole day.
Never Descend Downwind, whilst Decreasing airspeed. He appeared to be turning into the downwind direction.
The three D's - Drinking - Driving - Death.