If I understand you correctly, your hypothesis is that a COVID-19 vaccination, while it doesn't immediately kill someone, can cause conditions which lead to increased mortality.

With people still being re-infected by COVID, despite the pandemic being "over," could a COVID infection, itself, cause conditions which lead to increased mortality (for people who don't die from acute infection)?

I'm not proposing this as an either/or; I'm just saying that the vaccine wasn't the only change since 2020 :)