Myocarditis?
No. Myocarditis is an UBER painful inflammation of the heart. No one is running around a football pitch with myocarditis.
Upon autopsy they’ll likely find the surface of his heart riddled with patches of electrically non-conductive scar tissue. He is likely a victim of a viral or bacterial infection that migrated from his chest to the muscle tissue of his heart. Or in the case of SARS-CoV-2, perhaps an infection that attacked the lungs and the heart simultaneously.