Maybe the divers were trained for Deco and the accident was posting the question here.
I will give my not so sage wisdom and thoughts on the issue since it seems to be near and dear to my heart lately.
New divers can exceed the limits but I think it is rare, they mostly use there air too fast and watch their almighty computer really closely. many threads would prove this statistically.
when you have a few hundred dives I think the thinking goes something like "well it did not matter last time" what is a little deco, I am going to do a safety stop anyway just this one is required.
So the difference is not really inattention to gauges, because most people with hundreds of dives know what their air is, and about how much time they have left, they seem to make a conscious choice to ride the line a little tight because if they dont they will be on the boat with 1200# of air.
For me it seems important to think about the gear that people use to do Deco diving and how it is different from the gear that I usually wear on a recreational dive.
Double tanks? double regulators (4+ for the dive team), deco gas?
A buddy that is not only close but knows to look for me and knows how much air I have and my obligations and has reserve air for me.
the problem with accidental Deco is not the deco or the inaccurate computer used to signify it,
the problem is that if you have a problem and you have an actual deco obligation you may be totally and avoidably screwed without good backup planning and execution.
I have done it, I am not preaching, and I had a discussion with my wife on this last trip and we agreed that we would not accept any deco, and we still had a minute or two on one or two dives.
We had more than enough air to complete the obligation even if one of us had a total failure of one tank and as soon as I get within 5 minutes of deco I start swimming right next to her.
but with over 1k of air I am not going to stress too much if my wife wants to watch a ray on the sand for a few minutes, with one exception,
if I am about to go into deco at 35ft, seems the math is bad on this one, and the time required at 10 ft builds up fast really a bad idea.