It could easily have been a coincidence yes.
It's funny that you're spouting off about science, and then commit a fundamentally anti-scientific fallacy of correlation not being causation.
How quickly are you proposing that the mRNA in a vaccine could conceivably lead to sufficient damage to an individual's heart that it causes an infarct when it only achieves its full immunological potential in two weeks? Bearing in mind that it's only after a year of data collection that they're finding the possibility of negative consequences (and bearing in mind that these negative consequences are fewer and less likely than the Corona Virus itself).
Yes, science is fluid, but there are certain opinions that are fundamentally wrong, most of them based in old science, as it happens, and we can say with almost total certainty that they are wrong.