Are you done watching it? Good. Before we go on, I want to point out what wasn't said. He didn't say they had more talent. He didn't say it was genetics. He didn't talk about the sophistication of their training methods. He didn't talk about the quality of the coaching or their family support or their having more "desire". He does say two things, though, and they are actually related.
His first answer is that they have fewer mental barriers. So what does that mean? Sometimes a mental barrier can be a time (he mentions 13:00, a reference to the "barrier" he finally broke through in the 5000 meters). But it can also be a competitor (I can never beat that guy!), a superstition (oh man, I forgot my lucky water bottle!), or a lifestyle "need" (I would train more, but a guy's gotta work, y'know?). And of course there are numerous others, I'm sure.
The interesting thing about all these barriers is how huge they seem to people who can't get past them, and how trivial they become once someone has. I always think it's funny to hear about Roger Bannister suffering something along the lines of emotional exhaustion from the pursuit of the 4 minute mile, a time it was thought impossible to for a human being to run! Yet immediately after he broke the barrier, many other runners did, too. Now, runners who run the same time as Bannister are merely "very good".
Sure, the 4 minute "barrier" is still real for many runners, but it's not nearly as high as it once was. You could almost say it's more of a large stepping stone, now. That's why Kennedy's second answer is actually so much better in my opinion. He says runners aren't willing to turn their lives upside down in the pursuit of their training. They are unwilling to take some (necessary?) big risks.
It's very true. Most runners have a mental barrier in exactly this area. They can't imagine doing it differently, training somewhere else with someone else and so they settle. This isn't to say every athlete who sticks with his college coach is settling (Alan Webb just broke the mile with his high school coach, after all). It's just to say it's a barrier that many athletes aren't even aware of. It's a barrier that arises out of good intentions, even, whether it be loyalty, friendship, companionship, etc.
Barriers, for me, are a huge aspect of a person's self-efficacy, which I've talked about before. Self-efficacy is the belief in what you can do given the effort you put into something. One way to improve your self-efficacy is to experience success. Another is to have someone tell you that you can do it. But a third way applies even more in this case, I think. It is when you see someone you relate to break the barrier. It's when you effectively say, "Shoot, if he can do it so can I." It's when barriers the size of walls are reduced to stepping stones. We could call this the Roger Bannister Effect.
So here's the thing. Barriers are effectively mental roadblocks. Not only do they keep you doing what you are doing, but if they are tall enough, they keep you from even imagining being on another path.
I don't know all the reasons why Africa's elite runners seem to have so effectively removed mental barriers from their training. But I suspect it has a lot to do with the Roger Bannister Effect. Over the years, they've seen their countrymen--people just like them--break down barriers and they've gotten a glimpse of what it's like over there and what they need to do to get there.
Perhaps our American distance runners' biggest barrier is their inability to equate themselves equally with their African counterparts.