Honestly the research on exactly why this happens is sparse enough as it is. It’s basically impossible to do truly conclusive studies with tobacco because of how dangerous it is. We can’t even technically conclusively say that tobacco causes cancer because to truly scientifically assert that you’d have to do a randomized controlled trial. To have a truly randomized controlled trial you would have to randomly select people from the overall sample and tell them to start smoking for the purposes of the study (otherwise you can’t rule out there being some third thing that both causes the cancer and causes people to want to smoke). And because we know tobacco is insanely addictive and are all but that one millimeter short of proving that it causes cancer, no medical ethics oversight body would ever allow a study that requires participants to start smoking.