Knighton breaks the U18 record previously held by...Usain Bolt. Notice that the announcers are not even aware of the 17 y/o until the last few seconds. In 2024, he will still be only 20 years old.
Well, injuries happen. Bad training happens. Bad decisions and bad luck happen, and sometimes early promise does not materialise. But it does more often in track than other sports, because of the outsize influence of natural ability.