Now you are speculating about degree. But there are so many unanswered questions.
Is Kenyan prevalence higher as a percentage of athletes? Given the depth of distance running talent, the increase in athletes tested, and the increased testing, I would expect more Kenyans to test positive, even under the assumption of world-wide average doping prevalence. The steady stream of violations only tell me (along with the AIU) that Kenyan talent is deep and that testing has increased.
Regarding the connection I don't see, have you, or anyone, shown any connection between doping and elite distance running performances? How can I see what no one has shown? I will take your predicted non-responsive reply as a "no".
We see conceivable reasons all the time in these threads: it aids recovery; it boosts 20' cycling power and time to exhaustion; it increases VO2max and sub-VO2max on a treadmill; it increases RBC which can deliver more O2 to the muscles; etc. These substitute proxies are the wrong measures of elite distance running performance.
You still think I'm waiting to measure the "extent of gain" as if postiive gains have already been established for all dope for all athletes for all events in all states of training. Doping can be neutral and can even be detrimental to performance.
There is strong empirical evidence and observation dating back centuries and millenia of the correlation between training and performance. No one performs at the highest level without training. Training is one of the confounders to perceived gains attributed to doping.