blancolirio (active pilot who regularly makes videos about crahses with the aim of improving safety) just released a new video on this accident: https://youtu.be/_3gD_lnBNu0

Summary: The helicopter might have been a little bit too high. The night vision goggles might have negatively affected the vision. The two aircraft were probably on different frequencies so didn’t hear each other. And the helicopter might have focused on the wrong plane to avoid because they didn’t see the right one thanks to the city skyline. It looks like the classic swiss cheese where multiple problems stacked up to cause the collision. See the video for details.