That's my point. Coaches ARE already responsible for so much. They control the schedule, the training sessions, the traveling, they select competitions their athletes will participate in, they control the diet, the physio, the sports psychology, the choreo, jump content etc...
Do you really think they do not control what their athletes take for drugs? Valieva had a ton of authorized substance in her body as well... Drugs and supplements that very few 15 years old on the entire planet would have ever even needed or heard of. To think that it's the athletes popping a pill for fun once in a while and that it would be harmful for an innocent coach is really what is ridiculous to me. Coaches are well aware of pretty much everything... and if their jobs were at risk over doping, rest assured, they would make sure their athletes DO NOT dope.
Of course, some would still try to cheat the system

and these ones, once caught, would be penalized, not just their young athletes.