TV shows have a lot of content to get in a relatively short period of time and directing is an incredibly involved and exhausting job. The easiest way to accomplish this is to have multiple directors divide and conquer. Each director gets assigned an episode or two that they focus on for the season. The show runner will guide the directors in pre-production and often be on set to ensure the continuity of the look and feel of the show. TV directing is a somewhat different skill than directing features from that perspective.

A similar arrangement is often made with the Director of Photography, but it's also common to see one Cinematographer on the whole show which also helps to create consistency in the look of the show.

In my personal experience I've worked on shows that had multiple directors and multiple cinematographers. They would usual be paired up for their episodes. Often in these situations they had consistent camera operators across all of the episodes that ensured the visual language of the production was being maintained from a framing standpoint.