At his age, he likely had a congenital aortic valve defect. If he had aortic stenosis, that would cause enlargement of his left ventricle over time. He was young, but it is diagnosed in that age group. Sudden death can occur with aortic stenosis, unfortunately. Now, whether this was the case with this young man, I have no idea, but it could be the case.
The vax kills many organs and especially the heart.