During a normal Presidency when the POTUS becomes ill, it is announced by the Press Secretary, and the questions of the press are answered by medical professionals attending the POTUS. If the POTUS is anesthetized or in unable to carry out the duties of the office, as was the case when Reagan was shot, the VP takes over the duties for the few hours or days.

We can only look back fondly and hope in the future to see such normal times again.

Given that Trump has a mental image of himself as a 6'3" 230 lb. healthy virile specimen of masculinity, anything that doesn't fit with that vision has to be attacked, denied, or ignored. So what would make Trump disappear from public view for several days and be so embarrassing he has to deny it with the false narrative of playing golf?

Since the CDC has just tightened the ability of people to get COVID vaccines, I think Trump has COVID. It would not fit in with his ubermensch conceit, and it would make people have second thoughts about the vaccines they are being denied.