Hey, COVID=19 research scientist here. I am very sorry to hear about your your grandson.
Diagnosis: A heart defect. No sign of one when he was a kid. Strange.
Actually this is quite common. Many types of heart defects arent present or arent seen as a child but will as an adult. For example I have a type of defect that leads to a minor condition called PVC. While it is noticeable and diagnosable now doctors werent able to detect it till I was 30.
Problem: the number of young people in this situation is not trivial and either they are covering up COVID issues or they aren’t doing their research.
No one is covering up anything, though research is new and its possible we have a lot left to learn, that takes time, its not negligence. But your also making assumptions, you cant just assume every unusual event like a heart attack is COVID, it makes no sense, these sorts of things happened before COVID too.