Why does there have to be a hypothesis? Why can't it just be random? I understand the need to identify a reason, but randomness exists and there's a good chance that had more of a role in it than anything else.
Sure, it can be. But that's about as disempowering a thought as you can have if you need to try to live life as a cancer survivor. If you have any inkling that something may have contributed to its cause then you potentially have agency to help prevent it from recurring.