Again, that's misstating the science. No one could "learn" about cardiovascular effects of covid in 2021 because there was simply no consensus understanding.

"Doctors report many patients [...]" framing is true of all sorts of nonsense, all the time (including about covid! Hydroxychloroquine was being boosted by the same kind of anecdotal evidence). That's... just not how medicine works. How do you know which anecdotes are nonsense and which are correct? You do the science. And they did. But not in time for a lot of people, and yes, that's awful.