Being an avid runner or being a talented runner or being aware of who's who in professional running aren't necessarily related.
For those of Kip's friends or family that watched him run or dropped him at start lines, picked him up, provided fuel on the course or helped him retrieve discarded gear know very well that Kip had no access to cars, bikes or any other transportation, which made it virtually impossible to cheat, particularly in point to point courses.
It may be possible to fool a few people, but not thousands and certainly not his family and support crew. That kind of thinking is delusional. It is very telling that those who claim they want truth are suspiciously unwilling to contact the people who know the most, which are of course those who were actually at all these races with Kip.