TCAS adherence wasn’t fundamentally changed after the accident in question
yes it was. fundamentally.
at the time of the accident there wasn’t any regulation that would state what to do in case of contradicting instructions from tcas and atc. different pilots may have been and have been told something else, or may have not been told anything at all and left to make split second decision when such event occurs.
So let’s come back to the original argument: following the erroneous instructions of atc over the TCAS resulted in the accident
yeah, no. BEING SENT ONTO COLLISION COURSE is what resulted in the accident.
yes, had they followed the tcas, the accident might have been avoided. but that is not what caused it. they already were in the shitty situation when they had to decide between tcas and atc.
situation is caused by something that creates the situation, not by all of the infinite number of random things that might have been done to avoid it or escape it when you are already in. otherwise we could get into absurd argument like “if someone haven’t got out of the bed in the morning, the situation might have been avoided as well”. which, while technically true, is also absurd nonsense and no one would seriously tried to argue that.