From Kristina Wong via X: Spoke to someone who served in the same unit as the Army Black Hawk crew, knew 
them personally, and flew those routes. He made the following points:
1) That it was a training flight was not unusual at all. Those flights are flown everyday.
2) The co-pilot was going through her annual evaluation for night flying. Night vision goggles can magnify light, making it easier to confuse aircraft lights with ground lights.
3) Runway 33 — where Air Traffic Control told the passenger jet (CRJ) to land — is “rarely used.” This person said in his four years, he saw it being used 10 times. It is a much shorter runway than the main one used, which is Runway 1.
4) The Black Hawk appeared to confuse the passenger jet with another plane landing at Runway 1 — which is why the pilot-in-command confirmed seeing the CRJ and requesting “visual separation,” or essentially saying he would avoid it.
5) The CRJ was circling to land and making a left turn at the time. The Black Hawk was in its blind spot.
6) The crew was experienced: The instructor pilot had just under 1,000 flying hours. He was former Navy. The co-pilot had around 500 hours, and the crew chief — who served on multiple combat tours — around 1,000 hours. They flew these same routes for at least three years.
7) It was not unusual to have three crew members on a Black Hawk. There’s only four for certain mission sets. Whether the crew chief saw the CRJ would have depended on which side he was sitting on.
8) It was a dark night, with no moon.
9) Air Traffic Control could have told the Black Hawk to hold north, or diverted it.
10) Potential changes could be to change the route, altitude, or hours during heavy air traffic.
“All these things, they all made for the perfect storm.”