I think there needs to be a little nuance to the discussion still at this point to draw any specific conclusions.
First off - really hope the kid can pull through and get out of this alive. Just a terrible situation for obviously him, his family, and teammates
In general there were likely some mistakes made with this workout but until we know the actual level of difficulty, how all the players were reacting to it, health conditions, etc, its hard to say with certainty IMO to what degree everyone is at fault. I've seen it reported both ways that he collapsed from a heat related illness and also from a cardiac event so that aspect as far as I've seen isn't even certain. (and unfortunately it seems when most of these cardiac events happen it was unknown to anyone involved that the athlete was at risk)