Here's one way to look at it:
Many, many people smoke cigarettes, but only ~.003% of smokers develop lung cancer. However, 90% of cases of lung cancer are found in people who smoke.
Similarly, 10% of female bodied people have PCOS, but only ~.002% are trans. However, 60% of trans guys have PCOS symptoms.
While the link between smoking and lung cancer is stronger and more established, there is enough correlation to suggest a link.
ETA: As far as I am aware, no one argues anymore that smoking does not cause cancer, even though most people who smoke don't get it.