With the exception of, say, the first season of True Detective, most TV shows use multiple directors. The director on a TV show is usually in charge of the technical execution of the writers script - they’re not making many creative decisions the way a movie director does. The creative authority on a TV show generally rests on the lead writer(s), not the directors. When people talk about the Sopranos, they talk about David Chase; Breaking Bad, Vince Gilligan. And in both of those cases they had teams of writers under them who would write different episodes. This didn’t stop those shows from having a strong auteur-driven vision.
In the case of the LotR show, the lead writers are JD Payne and Patrick McKay. I think they’re passionate about Tolkien from what I’ve read. Look them up if you want to know more.