No one said it was on talent alone...it is talent and infrastructure. The European management agencies are investing in the training infrastructure that allow runners to succeed where AK is not. Management agencies provide training locations, coaching, physio, food, moral support, Pay for many of the athletes to travel to compete (at least when a runner is establishing him or herself. They are taking all the financial risk.
One previous poster tried to "prove" that foreign athletes must be cheating by looking at the number of sub 2:07 marathons since 2001. This poster asserted that there have been an explosion of sub 2:07 marathons since 2008 so this must point towards cheating. This is your classic "post hoc ergo propter hoc" situation (for all you Latin and/or philosophy majors)--just because something happens chronologically after an event does not mean (rarely ever means) it was caused by it. This is a basic logical fallacy I taught to middle schoolers back in the day. Just because times improved does not mean doping caused it. As a point of reference look at the "explosion" of new sub 4min milers in the us since 2001
http://www.trackandfieldnews.com/index.php/category-lists/1476-tafn-us-sub-400-milers
. Does this "prove" Americans are doping?
The fact is, these management agencies are investing more in the training infrastructure as a result of expanded purses in international marathons. It is no longer just the majors, it is seoul, mumbai, portugal, the rock and roll series, etc. Since managers are investing more in terms of coaching, physio, etc it should not be a surprise that the times have become more competitive.
To suggest that this "proves" (or at least suggests) wide spread cheating, doesn't understand all the factors that go into developing a successful stable of runners. There can be a myriad of causes.