“The story material that we got from Part II of the game is way more than the story material that was in the first game, so part of what we had to do from the start was figure out how to tell that story across seasons,” Mazin explained. “When you do that, you look for natural breakpoints, and as we laid it out, this season, the natural breakpoint felt like it came after seven episodes.” (Season 1 clocked in at nine episodes, for comparison.)
The good news for fans is that even though HBO has yet to confirm additional seasons, it sounds like Mazin is pretty confident that more are coming. “I don’t see how we could tell the story that remains after season 2 is complete in one more season,” he explained.
https://www.theverge.com/2024/6/5/24172396/the-last-of-us-season-2-episode-count-hbo