https://www.youtube.com/watch?v=_3gD_lnBNu0
If you got 11 minutes, this is an excellent video by an apparently knowledgeable individual. If he is right, several things could have contributed to the crash - mistaken aircraft identity by helicopter, helicopter being 100' too high, possible use of night vision goggles in that situation, plus a few others.
Could be a typical swiss cheese model where several factors lined up but none in themselves would have been fatal.