Vaccination conundrum?

https://www.channelnewsasia.com/news/singapore/covid-19-vaccine-72-year-old-man-cardiac-arrest-ttsh-moh-14228104

I don't know whether the covid vaccine will induce a heart attack or not but I do question the medical logic.

Here's my conundrum:

When you have a pre-existing illness and you get infected by covid and fall sick, the medical expert will say that your sickness is due to the covid virus and not your pre-existing illness.

When you have a pre-existing illness and you fall sick on the same day after getting a covid vaccination, the medical expert will say that your sickness is not due to your vaccination but due to your pre-existing illness.

I'm so confused! Sigh!