We can’t know at the time that a record is unbeatable, we can only suppose it in retrospect once a record has stood for years or decades. And even then it might be because we’re still waiting for as rare a talent as the current record holder and that takes time.
It may also be that the sport itself changes over time in some small way that puts old records out of reach, like the multiple times they nerfed the javelin to keep the throws safely inside the running track.
Latest Answers