I'm on that part of the water frequently and see the process from sea level. It seems orderly and safe on any given day. Tragically what may have happened is a deadly cocktail of commercial pressure, complacency and long days of flying. Keep in mind this would have been one of the busiest days ever for this operation coming out of Covid and with a 100 % fleet increase. The challenge was to get through as many flights in a day. The descending helicopter would have had the departing one on the left and below it, thus obscured. The departing one likely would have been able to see the other one on his right and above, but with no 'relative motion' likely would not have been picked up in his peripheral vision. These guys do this dozens of times an hour so radio calls are likely to be perfunctory as all pilots expect they know what the others are doing. Throw in complacency from doing the job repetitively day in day out and it's a very tragic outcome.