Was Chomsky ever an expert? Maybe, I wouldn't know because I haven't read what he built his legacy upon. But that he wrote so poorly on two topics he has little experience with does him no favors.
Chomsky is a Linguistics Professor, he has no formal training in media or political theory. So yes, he is not an expert, and funnily enough he's the kind of leftist who straight up admits he is biased and selectively picks facts to support this arguments.
My entire life anything I hear from him has been misinformed and anything I hear about him is "Chomsky disproven". I have to imagine whatever he was known for happened before I was born - which I've never been exposed to. Granted I've never sought it out either.
To me he feels like an academic Kardashian: Famous for being famous, and it's not really clear how it started.