According to the folks who did the recovery dive, even if Spivey and his son had made it back to their staged bottles, they would not have had enough gas to do the required deco for the time they had spent at depth.
I am an avid cave diver, and I even have a technical cert. I do not do significant staged decompression dives in caves, and I suspect I never will. I don't cave dive or tech dive often enough to be sharp enough to do Eagle's Nest. I have repeatedly refused invitations to do Indian, which is a far less technical dive, because . . . I'm not good enough.
In this case, we had a father with no cave training, and a son whose only training was done by the father -- who obviously taught his son well, as far as he knew to do, because the two of them had been cave diving repeatedly, including prior dives in Eagle's Nest. (This is actually all well documented on line.) The problem appears to have been that the father didn't know as much as he thought he did, and he trained a son with the same holes in his understanding. They appear to have ignored two very basic concepts -- control of narcosis in a cave (and although many people espouse deep air diving in open water, I know of NO ONE who does so in caves), and adequate gas planning, including contingencies.
I take a couple of things away from this. One is that, as always, diving is great so long as nothing goes wrong. These two had spun the revolver in Russian Roulette a number of times before, and as so often happens, had become convinced that their failure to land on the full cylinder meant it would never happen.
The other thing is that you should be very careful who you teach, and what you teach -- because any gaps in your own knowledge or skill are simply going to pass along to your student. If they don't kill you, they may kill him. Classes have curricula because the information is felt to be IMPORTANT -- anything left out is a potential problem at best, or accident at worst.
I feel incredibly sorry for the recovery divers, one of whom is being pilloried on multiple boards for having been aware of the activities of these two, and having failed to stop it. How do you stop someone from doing something stupid, if they are hell-bent on doing it?
"Sometimes, when your world is going sideways, the second best thing to everything working out right, is knowing you are loved..." ljjames