So here is my offering on the chain of events after viewing a lot of the available news reports and interviews and presentations with aviators, both fixed wing and helicopter:
(btw, I have never been a licensed pilot, I have thousands of hours as an Airlift and Special Ops Navigator, and a lot of time flying with crews using NVGs, although 30 to 40 years ago).
My eagle eye view (using google maps) is that it's about 2.5 nm from the Key Bridge (permission required to cross, by Tower) and hearing that the Blackhawk would be traveling at about 120 kts, so that's about 1+23 minutes, give or take, before they would intersect the rwy 33 approach course. I was surprised to hear they were moving that fast. I would have guessed maybe 70 to 90 knots, but I have only been a passenger on helicopters.
The tower's release of the Blackhawk to proceed didn't really account for the arrival of flt 5342.
The Tower controller needed to hear the "in sight" response from the Blackhawk. Fine. It's all good. PAT 25 never had the correct aircraft in sight.
5342 didn't hear the conversation between Tower and PAT 25.
Thank you to coconutEd and tk for tu juan (see page 27 of this thread) for this:
IDEK is 1.61 miles to the threshold of RWY 33.
I would just imagine that the pilots of 5342 were just happy as can be to fly a visual approach, considering their normal day as airline pilots. I am not familiar at all with the modern days of RNAV and GPS, but I think that approach from Rwy 01 to 33 becoming a visual approach meant they had the navigational data to known when to start their turn and at were 490' or higher.
From my ancient days, I do remember the 300' per NM descent rate. (I did design and navigate many an airborne radar approach using a ground mapping radar, the curtain pulled to keep a dark cockpit, all the Pilots and Flight Engineer and Map Nav on their NVGs, landing on blacked out dirt or paved runways.)
So if the CRJ was descending at 300'/nm or more accurately 320'/nm using the VASIs, it seems they would be at approximately 233' MSL when crossing the river. Pilots, please correct me if I'm wrong or if they would be aiming further down the runway, but I'm guessing they are aiming to put it down as soon as practical.
PAT 25 could very well have been pretty dang close to 200' agl.
The Tower did not stop the helicopter and airplane from intersecting. The helo had no way of spotting 5342 way off to their left, (especially while on NVGs). How fast was 5342? Maybe 140 kias? PAT 25 - 120 kias? And they could have been within 50' in altitude.
So my theory is 5342 banked left a split second after seeing movement to their right. A blink of an eye.
VAT 25 also saw nothing to their left, and in an instant it got blindingly bright and their brain(s) pulled the collective , but all that happened in an instant.
I've seen this happen in flight - a copilot is flying on a peaceful day in the Bering Strait and glances off to his right, sees a MIG on our wingtip, and violently banks to the left, purely on instinct.
I've been out there over the water at night at maybe 2000' , in a right hand orbit, and swoosh. The pilot flying never even had an instant to react. We were lights out. A very large aircraft went through our windscreen from right to left, also lights out. Someone forgot to deconflict us. It was over before you could think. (Except going through their wash and rolling maybe 70 degrees to the right.
Thanks for reading. Hope it didn't bore you too much.