Probability means that it’s a game of chance, but lots of things can affect the likelihood of each outcome. A perfect die would mean that all six outcomes are equally likely. A weighted die makes some outcomes more likely than others, but all outcomes are still possible. There’s still a whole lot of chance involved even when the odds are not even.
The actions of cells and molecules are very stochastic and chaotic (meaning the mathematical term of chaos). So-called “cancer-causing” chemicals, genes, lifestyles, etc., merely affect the odds. They are not direct cause and effect. It’s not either-or, it’s probability.
Every time a cell divides in your body, it is rolling the dice and flirting with the possibility of developing cancer. Early stage cancers actually occur in your body quite frequently, but mostly fail to develop into full-blown cancer. Who gets cancer and when (and which kind) is largely up to chance, but things like smoking, UV and X-ray exposure, obesity, and poor diet can definitely affect the odds. It’s like “weighting the dice” to make some outcomes more likely than they would have been.
The odds are greater if you smoke, but non-smokers sometimes get lung cancer and heavy smokers sometimes don’t. Again, this is something that has been known for some time. The word “luck” is misleading, but it’s very true that random probability is the biggest factor in the development of cancer. Maintaining a healthy lifestyle, weight, and staying as free from carcinogens as possible truly does give you the best chance of staying cancer free until a ripe old age. But there’s still a lot of “chance” in the equation. You can do everything right, but still get cancer. You can do everything wrong and still not. But the CHANCES are lower when you live a healthy lifestyle.
It’s like betting at the horse race. Yes, the longest-odds horse does sometimes win, but the smartest bet is still on the fastest horse, even if it doesn’t win every time.