The simplest explanation is that they dope, and it works.
Other explanations are byzantine and convoluted, exactly like the explanations offered by bodybuilders.
Both the bodybuilding and the European-coaching-African-distance-runners invent these giant structures of fantasy to take the place of a simple, obvious, and proven explanation. There's always some "secret" that they're not willing to reveal, because it's proprietary, or because there is some privacy concern, or because they want to stay a step ahead of their competition...and according to them the secret always involves some new and complicated training modality, location, monitoring, periodization, whatever.
And they go to great lengths to make convoluted, yet unconvincing, excuses for all of their partners-in-crime, even if on the track they are their competitors.
Dietrologia, the idea that the explanation that is visible, obvious, and proven (PED's) cannot be the real explanation, that there has to be "something behind" it, like a new super-secret and so-complicated-that-you-would-have-trouble-understanding-it training methodology.
Like all B.S., an ever-increasing web of lies and fantasy are required to maintain the increasingly complex and unstable edifice of "what lies behind".
The key, to make it successful, is to know your audience, and to play to their biases and weaknesses. The track community desperately wants to believe that their heroes are clean, and will entertain the b.s. It's a perfect setup.
Make no mistake, everybody in Italy does this kind of thing, about all sorts of issues. They have varying audience sizes, most often their small circle of idiot friends.
I have heard it described as the second biggest Italian pastime...second only to football.
Canova, the unmasking is complete.