You’re confusing mild cases with severe cases. Show me one story where a mild case had a flare up 10 days after symptoms. I looked there are none.
Out of every 100 cases of those over 70 who get the virus, 10 to 15 persons may be expected to sick enough to be hospitalized and 5 of those cases may be expected to be fatal. About 90 percent who die will have had pre-existing co-morbidities that exacerbate and contribute to their deaths.
Trump has not had a crash and die and he has a 95 percent chance that he won’t. Perhaps he has an even better chance that he won’t due to his excellent health.