Sven 62: When you flare at the bottom of your auto (even in this case) the Nr increases, not decreases. So assuming he misidentifies the landing surface and flares harder to "gain height", the Nr will rise. He may well then drop further before landing, but the rotors will still retain enough momentum to disintegrate on impact with the back of the cab/other objects.
I was postulating that, being out of options and already well into the touchdown flare, the lever was being raised rather fast to get over the obstruction, hence Nr drooping mightily despite the flare effect. It is speculative. Autos at night always scared me, even with NVG and an airfield underneath and all the time in the world to set it up for training. I take your point about residual rotation smashing the blades. SOMETHING reduced that to a negligible effect. If not the last vestiges of cushioning, then what?