I know 2 people - 4:05 and 4:20 - who have run about 14:40 in the 5000. They train together but how are their miles so different yet their 5000 is the same (basically)?
Maybe the 4:05 miler is doing more work in the weight room that's making him faster in the mile but it's not translating to 5k. That might explain some of the difference. But most of the difference probably comes down to genetics. Someone with more fast-twitch muscle fibers will do better in the middle distances but that won't always translate to the longer distances.
I know 2 people - 4:05 and 4:20 - who have run about 14:40 in the 5000. They train together but how are their miles so different yet their 5000 is the same (basically)?
And there are guys like Young that have enough speed to approach a 3:50 mile, and the strength to run sub-27:00. It all comes down to genetics.
His PR is 3:54
His 1500m 3:34.56 PR converts to 3:51.7, and I seriously believe that if he gets another chance to run a 1500m, or a mlle, this season, he can improve by another second or more.
The answer is obvious as many others have said, we're all different and have different athletic strengths, but to add an example: in college my senior year I was our team's top guy in 3000/5000 and cross-country. We had a guy who would be number 2 or 3 in XC but who could dust me in the 10,000. He could hang close to me in the 5000 and my PR was only 5 seconds better than his. But my PR in the 800 was like 7 or 8 seconds better, and my 800 was not impressive by any means. He just literally had no speed at all. He later went on to absolutely crush a few marathons post-college, which was no surprise to any of us.