There is so much light pollution there, it would be easy to miss that UH 60 amongst the clutter of DC off to the jet's right. And during landing, I'm sure the pilot and crew are focused on plenty of things, and not checking left and right for possible collisions.
And no, not all investigators have been fired, FFS.
VG, yes, done DCA as a pax many times (not quite as many as you) and also flying. The light pollution in the DC area is horrendous. Having flown there (DC and Fort Belvoir area) I’d actually prefer to fly down the Hudson or East Rivers in NYC, over DC.
See and avoid is a responsibility to all aircrew,
however, ATC gave DIRECTION (in KDCA’s positive control zone) to PAT25 to proceed Southbound BEHIND AA5342, which was cleared to land on visual final approach to RWY33. The AA5342 crew were on very short final, within 10-15 seconds of touchdown, so without doubt the captain and first officer would have been focusing on the runway environment to land, and not off to their 2o’clock masked by the U.S. Capitol and FBI HQ, etc. For PAT25’s part, at that altitude on short final, AA5342 would have been backlit by a long wall of hotels and building in Crystal City, making visual identification difficult. Further compounding this is that aircraft on a collision course with each other do not visually move relatively in each other’s windscreen, they only get larger. The human eye is fairly decent at detecting relative motion, but incipient ‘static’ (relatively) growth of an apparently non-moving object is much harder to detect.
The NTSB investigation will analyze cause factors as to why, but factually it is clear the PAT25 did not proceed behind AA5342 as directed. No doubt there may be more regulations/procedures regarding flight ops in the DC area to come out of this, with an aim to avoid accidents like this in the future.
An absolute tragedy to be sure!
Edit to add: Will leave this here, but same link as Baz provided.
Not sure if the link will work, but an interesting view of the final secondary radar of DCA and associated ATC and pilot comms, showing the paths of AA4532 and PAT25.