How did I get breast cancer at a young age?

I know the cause of getting cancer is really unknown, but that if you have the breast cancer gene, then you are predisposed to getting it. Because of my lack of family history (other than my paternal aunt getting the diagnosis when she was 60 years old), the doctors wanted me to get the genetic testing done which I got done a couple weeks ago. I just got my results back showing I have no BRCA gene. I’m currently 23 years old and I feel like I have done everything lifestyle wise like every other 23 year old (smoking weed, trying vaping, etc.) , but nothing crazy or addiction wise related to a super “unhealthy”lifestyle. Just wondering if anyone else can also relate to this and if it was really “the luck of the draw.”