since his health is of no consequence whatsoever.
Uhm yes? That is the entire point. It is a stressfull job and you need to be at full mental and sufficient physical capacity to handle it. Biden showed that he is not up to it anymore. Trump also is starting to show signs of decline, but he is further ahead of the curve than Biden is.
Either candidate is unfit for office, but for Biden health is the crucial issue. And old age is not something you can recover from. Just statistically it is entirely reasonable to expect either one of them to die in office.