Those who are using these sort of incidents to try and push their agenda ought to be ashamed of themselves. Some could be vaccine related, some could be as a result of a past Covid-19 infection, but most will probably be completely unrelated to Covid. Stop trying to score cheap points.
Watching football (as a fan) is a small, but statistically significant known risk factor for heart issues - the incident of hearts attacks rises in an area immediately after the local team loses. Having seen how some people get worked up during a game, it is not surprising if those people have health issues as a result. And as others have mentioned above, the clubs are reacting quicker using their doctors and support staff to deal with the ill supporter until they can be taken to hospital. Without a club doctor available, this is an increased risk factor for the players who the clubs have a duty of care to and so the game now pauses while the doctors are available again.