Moved into new (to us, built in 1980) house 2 years ago. Installed an Airthings radon meter a year ago. Levels get up to 400 Bq/m3 when all the windows are closed. Finally had a radon mitigation system installed. Will hopefully get to much safer level below 100 Bq/m3.
You don’t live on a thin crust of a planet of molten stone?
NW Florida is mainly 1" of topsoil and then a sandy red clay mix all the way to China.
The South, except where the last of the Appalachians dip in, is basically radon free.
https://www2.lbl.gov/Science-Articles/Archive/images2/radon-map.gif