and became visual at 6,000.
You couldn't go below FL160 unless you were visual so the above doesn't apply.
You could only leave FL 160 if you we visual, and then you could descend to 6000ft while maintaining visual.
That's it.
The argument that "everyone else did it" has it's place, but not not in absolving the Captain of responsibility. It's place belongs in the discussion of 'company culture'. If Collins was heavily influenced by the actions/words of his superiors and colleagues then he is completely normal, so we have to look at how seriously we take the development and maintenance of these cultures, because 99% of us are susceptible to the influence they wield. The CEO's and department heads in our organisations need to be aware that they are responsible for the 'safety culture' and that they need to control the direction it is moving, this will be uncomfortable for them as it may make it difficult for them to achieve some commercial targets, but that is the cold hard truth. I would go so far as to say that the 'safety culture' needs to be monitored.
Either way, Collins, who I assume was a good man, dropped the ball. The fact that he was let down by others around him does not absolve him of his responsibilities. That's life, now we need to look at why we haven't learnt from it.