I flew with Collins about two weeks prior to the il-fated 901,and admit he was a pleasant fellow to fly with, but there was a hard nosed streak, that occasionally showed up.
Cassin was at the other end of the scale, a very pleasant and mildly submissive.
Another thing that could have had a bearing, but should not have had, was that Collins was ex Air Force, and Cassin was Aero Club trained.
By what company directive were they enabled to descend to the company advertised "see Antarctica from 2,000 feet". The advertised 2,000 rather puts the contention that 6,000 was the limit in some doubt.
That was a requirement by CAA, not below 6,000ft. It of course had been broken a number of times, but all after being identified by McMurdo radar, and in real .VMC conditions.
Nevertheless, it was a requirement as laid down by CAA before these flights were commenced. As has been said on this thread a number of times, CAA denied having any knowledge of these indiscretions. As there were no repercussions from CAA the practice continued.
I can add now in hind sight that the mindset of many of the the then Captains, and even right up until 1980's was of unmittigated omnipotence
That statement, made of some of those people at the time, might explain why the rules were disregarded.
If you want to break, or disregard the rules, and have the end result this crew had, and then we get the findings of Mahon that the crew were blameless, this discussion will go on forever.