I think what you’re referring to is the notion that many men after they die are discovered to have prostate cancer on autopsy. In a normal setting, prostate cancer is very slow growing and never leaves the prostate. In a case like this, a man is much more likely to die from other causes rather than the prostate cancer. In fact it is often said that men over the age of 80 die with prostate cancer not from it. The cancer cells are very slow growing and never become a significant health risk for that individual.
Prostate cancer has become a huge epidemic and we often only hear of the stories of men who have suffered from a more aggressive form of the disease that happens earlier in life. Some older men can develop a more aggressive form that is life threatening. These more aggressive forms are related to a series of predisposing risk factors such as genetics, ethnicity, poor diet, excessive weight and possibly a correlation to higher exposure to hormones in our foods and environment.
So yes, it is true that many men die with a type of cancer but that cancer is not posing a significant risk to their health.