If you get a disease that you wouldn't have gotten had you not consumed alcohol, then the alcohol consumption is the root cause of your disease. The study found 61 diseases for which this is the case for different people
As I said, the root cause of many people's heart stopping has been a bullet passing through it - those people's hearts wouldn't have otherwise developed massive holes and would have gone on ticking had it not been for the bullet - but that doesn't mean that bullets piercing hearts is the exclusive reason that hearts stop.
I'm not sure if the point you're trying to make is that not everyone who consumes alcohol gets these diseases or that alcohol consumption isn't the only cause of these diseases. Both of those statements are correct but neither are contrary to the study's conclusion.