That sounds wild. I don’t know where you are but in the USA you could reach out to a university extension program/office and ask them to look into it. It’s bizarre enough to catch their interest and come at no cost to you.
Edit: it really is bizarre because Radon is primarily produced by reactions underground/in the earth and has a relatively short half life (3.5 days). I don’t see how it could be atmospherically sourced without it being a hazard to the whole community, regardless of the bizarre convection currents that bring it into your house. It’s unlikely to be produced in your attic.
If I were you, I’d want to know more and understand how this is all happening lest you raze and rebuild and find you still have a problem.
