So, at about 4850' amsl, assuming 1013.2 at sea level, that would give about 6000' DA at 15 deg and 6500' at 20 deg.
The very light tailwind may have been a minor contributory factor but it begs the question of handling skills - not making an approach to an IGE hover - and performance calcs - how heavy were they for what they were trying to do?
As aerolearner questions in his OP - was it LTA/E caused by an inadequate TR?