Upon realizing that the helicopter would not reach the runway, the pilot could have landed straight ahead and touched down prior to the runway or performed a 180° turn to a field directly behind the helicopter; however, he continued the approach to the runway and attempted to extend the helicopter's glide by increasing collective pitch, an action that resulted in a decay of rotor rpm and an uncontrolled descent.
Helicopter Pilots live and die by Rotor RPM.
It is fine to have too much but fatal to have too little.
Dragging down the Rotor RPM to "stretch the glide" can kill you if you get below the Minimum Power Off Rotor RPM Limit determined by the Manufacturer.
Far better to wind up in the Trees with bags of Rotor RPM to cushion the touchdown than to crash in an open area without any.