Sometimes it is just bad luck.
Sometimes it’s genetic.
I am sure there are environmental issues ( drinking, diabetes, etc) that could have a correlation.
My wife just had bad luck.
So genuinely sorry tolearn about your wife. Best of best luck to her.
My wife never smoked, but got lung cancer. May be growing up in a family where dad+mom+4 siblings smoked may have someting to do with it. Or living many years in basement apartment in Chicago where radon levels are known to be high. No one knows. It is almost 5 years since diagnosis, and she is a fighter.