There is a mix of reasons, one is that for more than a year, people were locked away with TV/internet and shitty instant food, which does miracle for ones health, not to mention that all the stress from media propaganda about pandemic also takes toll on the body, then there is the fact that due to kung-flu all regular medical work was cancelled, so hospitals are now being hit by waves of people who missed diagnosis and treatment until dire symptoms showed up.
As for young people dying of sudden heart problems, it happens, although rarely and it could be also chalked up to cancelled medical work, however heart problems are also known side effect of the kung-flu vaccinations, but medical establishment staunchly refuses to recognise any such issues.