Sorry to burst your bubble, but the reason Kenyans dominate at long distance running is that their national ADA (anti doping agency) doesn't enforce the rules.
Is it bad form to quote myself? it seems likely that drugs have been a factor in the increased speed of distance runners. Sadly, the testing procedures for athletics are notably worse that for cycling
But there is more to Kenyan domination than just doping. For example, there are plenty of countries with a history of distance running which are known to have weak anti-doping policies, and yet they aren't competitive anymore.
No, the reason they dominate marathon running is because prize money is huge (by their standards of living) and has exploded in the last 30 years. Americans and Europeans have gone BACKWARDS since the 80's, as the sport is longer popular.
Here is an actual informative documentary (unlike your article which reads like it's from TMZ):
Your article doesn't talk about any top Kenyan runners. The only Kenyans that have been caught doping in recent years (yes they do get tested) are third-tier Kenyans, usually without education, thinking (or being persuaded by doctors) that it will get them to the top level, which it never does.
I don't see any evidence that Kipsang, Kimetto, Mutai, or Makau ever used drugs, or anyone even claiming to be in the know that they used.
But there is more to Kenyan domination than just doping. For example, there are plenty of countries with a history of distance running which are known to have weak anti-doping policies, and yet they aren't competitive anymore.