Being a functioning alcoholic is a thing. I've known two people who were self-described as this, got help and are now both sober. One was a friend who was a lawyer. He obviously wasn't drunk in court or even going into the office, but he'd tie one on a lot of nights. He said he started drinking so much he was regularly blacking out. He said only a handful of people he worked with knew what he was struggling with and he'd be surprised if some of his co-workers ever knew he was alcoholic.
The other one was a woman I worked with a decade or so ago. She was very nice and somewhat soft spoken. She was always at work - outside of seeing her at an occasional happy hour I never would have guessed she was an alcoholic until she shared her story on facebook.
Long of the short of it, I think some people are flat out wrong in thinking an alcoholic is an always drunk, stereotypically hungover mess. Sometimes people are good at hiding it.
That said, I'm with you. I've seen reports that Hegseth is an alcoholic, but I don't know for sure.