https://www.ncbi.nlm.nih.gov/books/NBK279364/

As long as your immune system is running smoothly, you don’t notice that it’s there. But if it stops working properly – because it’s weak or can't fight particularly aggressive germs – you get ill. Germs that your body has never encountered before are also likely to make you ill. Some germs will only make you ill the first time you come into contact with them. These include childhood diseases like chickenpox.

Covid falls into the the category of germs that your body has never encountered before. As such unvaccinated people had effectively no defense against it. But sure, downvote me because you don't like actual scientific facts clown.