Blackbird
but it's early days for speculating too deeply about the exact cause of this disaster.
No. Unlike the Jeju crash that has multiple major unknowns, for the most part, this is a very clear cut case.
The weather was good and there is no evidence of any malfunction, so it comes down to mostly human 'factors'.
The AA flight was most likely already on an ILS glide path to runway 33 and as far as we know they didn't do anything wrong. I'm not sure if they were aware of the presence of a nearby helicopter, but it would be the controller's and helicopter pilot's duty to ensure safe distance, especially since the helicopter was flying, at least initially, beneath the airplane, and the pilots in the airplane normally cannot see what's underneath them.
The helicopter pilot knew about the landing airplane, supposed to have a visual, and was supposed to keep a safe distance. We can't be 100% certain if he had, or not, a visual of the correct airplane, but he most certainly didn't keep a safe distance.
The controller trusted the helicopter pilot and allowed it to fly on a potentially intersecting path. Whether the controller could've or should've done more to prevent this disaster -- that I do not know since allowing helicopters seems to have been a normal modus operandi there.
Lastly, the likely lack of TCAS on the helicopter. I can fully understand if military airplanes don't use it in war zones, but the area around DC is not supposed to be a war zone.
No source was provided but this is rather damning: https://x.com/Turbinetraveler/status/1884834926781956420