Saving a penalty kick can involve a strenuous dive to one side or the other, unless he outguessed the shooter and stayed in the middle. In that case he could have taken a hard shot to the chest. Either way, that or the strenuous dive could put strain on the heart, even though, as somebody commented, soccer goalies are not running very much during the game, compared to most of the other players.
The frequency of this has definitely gone up in the COVID era, among athletes, whether it’s the same for the general population. I suspect the rates are higher in general, but perhaps not quite such a large increase.