How does a collegiate athlete die of a heart attack?
I mean, they surely have to pass a physical right?
Because the human body is far more complex than than we are currently able to comprehend. These things simply happen, it isn't a failure of the doctors performing the physicals, it is nothing more than the body doing what it is going to do.
As for the physical, they do not call it "practicing" medicine for nothing. It is a constantly evolving experience.
You could ask, how does a person who smokes, drinks whiskey daily, lives on biscuits and gravy and spend the majority of their time watching The Price Is Right live to be 95 years old, but this also occurs.
It is a tragic thing to experience, I hope the family and friends remember him fondly and cherish his life for what it was.