How did i get kidney cancer?

Difficult to be sure: Most kidney cancers are sporadic, meaning there is no inherited cause, though there are a number of familial syndromes associated with it. Multiple factors including environmental exposures and possibly diet smoking and obesity can lead to genetic mutations in kidney cells which if not properly repaired can lead to uncontrolled growth sometimes with the ability to spread far from the kidney.

Bad luck: Sometimes, it's genetic. But most often, it's random.