I know a lot of professionals who use drugs responsibly and recreationally. Even the ones who use hard drugs or abuse alcohol heavily tend to walk the fine line between functional addict and basket-case. Of course, there's a survivorship bias to my anecdotal evidence.
I don't smoke pot, but I think it's one of the least harmful drugs if someone enjoys getting high regularly. Physical and psychological dependance are rare, the effects are mild for most people, and it isn't especially harmful to the body (at least if you vaporize or eat it).
It may be that drug use and maintaining a professional career are simply not related.