The crux of it:
Caught Covid in January, gave it to Mia because she refused to not be there for him costing her a spot in the Rumble.
Came back for the match against Riddle in February, next day got a call saying something was off in his blood. Caused inflamation of his heart. Wasn't allowed to train or any activity outside of a light walk.
-----
Basically what most people were saying, caught covid then had complications following it...