I can only go on what the 2 brothers have told me ( I taught them both not only Ppl but conversion as well )
Coming into land in a field ( 300m x 300m ) gone over a set of low level power lines to a house ( all other 3 sides have tall trees ) with wind on left shoulder. The idea being to turn ac into wind before losing translational lift.
I can only assume they lost translational lift at the same time as starting to pull power in which further reduced speed ( so double whammy ). They say they were doing about 20 kts over the ground. The 500 has a powerful tail rotor on a short tail boom, so you really need to get pedals in early. So can only assume ( dangerous I know ) they didn't put enough pedal in. Normally the pedals will sort it so very surprised that it didn't. Did they put enough pedal in I don't know ? The other brother said the ac snapped right then back to the left ( twice ) before spinning 4 times ( the other brother said it didn't ).
PF then decided after 4 spins to close throttle as things were getting out of hand !
As with all these things there by the grace of God and difficult for us to make a judgement from an arm chair