It's resources and what sport most people prefer to play. In my high school our best track athletes didn't even run track. Some of them would wait until their senior year when football season is over and they had nothing else to do but graduate and then decide to come out for outdoor. The track coaches would always be
at why these nikkas waited until then to actually try. The nikkas that did take track more seriously than them were much smaller and were mostly football rejects. They played jv but saw there was no future in it for them so then they take track more seriously their sophmore year.
Look at Devon Allen from Oregon, he also plays football. He's the U.S.'s best 100m hurdler and placed 5th in Rio. Imagine if he said fukk track and focused on football, we'd never know he existed. But also imagine if he said fukk football and put more effort into track, it's possible he'd be much better. All those hits and nagging injuries carried over from a 4-5 month football season likely effects his training for track. But here's the other thing, if you look at him and his stature, I'm almost certain you can find better "athletes" than him on Oregon's team alone yet those guys likely never gave track and field a shot because their focus and commitment was 100% to football. Maybe they may have dabbled in it when they were younger to stay in shape and workout in the offseason, but it's def not anything they took seriously.
Compare Devon Allen's stature to the guys who beat him, and compare those guys to other players on Oregon's team.
Here's Omar Mcleod, the Jamaican gold medalist compared to Devon Allen. Allen physically isn't all the way there with Mcleod. Bigger thighs, broader shoulders, more muscle definition. I'm sure you could find some guys on Oregon's team that match up better physically to Mcleod than Allen. However those guys likely never cared or even thought of competing in this event.