According to the undisputed facts they were all on a line in less than 15 feet of water. How hard would it have been to simply keep them together?
Somewhere between difficult and impossible.
Given normal distances and human reaction time, by the time the instructor figured out that something was going on, it was already too late to keep them together. Someone would need to be chased and someone would need to be ignored.
Taking the two boys up the line with the instructor at a safe ascent rate would have taken all of 15-25 seconds.
The ascent could
maybe be done that quickly once it starts, but getting them to understand what's going on takes time too, as does starting the ascent and controlling their buoyancy. Then you have to make them positively buoyant on the surface and make sure they're OK and communicate that they should stay put.
Then you abandon them on the surface (another "violation"), and look around for the participant who bolted and handle that emergency. By this time, it's entirely possible that the original victim may have surfaced, panicked or passed out, and re-descended.
Even times when I've already been on the surface, specifically watching for problems, and ready to assist, once someone pops up, there aren't a whole lot of seconds before they go back under, especially if it was from a medical problem.
The real answer is that more than 1:1 simply isn't workable.
And again if the parents lying about the child's acute asthma on the Medical forms turns out to be the trigger event- NOTHING else done or not may have mattered.
I'll give you partial credit on that one, although even asthma is better handled when there's nobody else to worry about.
flots.