Bran Stark became King in Game of Thrones' ending, but the real mistake with the character happened years earlier. The Game of Thrones series finale was controversial for several reasons, including the death of Daenerys Targaryen at the hands of Jon Snow, but one of the biggest points of contention was Bran becoming King. It was a decision that came out of nowhere to many viewers, since Bran had largely been separate from the great game surrounding the Iron Throne, and so factored heavily into the backlash to season 8.
Whether King Bran was the right choice for Game of Thrones' ending or not, it wasn't the biggest mistake with the character. Instead, that came when Bran was entirely missing from Game of Thrones season 5. Despite being among the main characters, he didn't appear at all that year, which ultimately hurt his arc and ending. It meant skipping past some of his Three-Eyed Raven training, and by the end his powers weren't explained or defined enough. Similarly, it robbed him of a chance of more character development, which could have improved his ending further.
Why Bran Was Missing In Game Of Thrones Season 5
Game of Thrones season 5 represented the crossroads where the show started to catch up with and, in some cases, overtake the books. Showrunners David Benioff and D.B. Weiss had some big decisions to make, and that included having no Bran in Game of Thrones season 5. They explained that because Bran's story in season 4 had largely caught up with the books, "if we pushed him forward this season, then he’s way ahead of where the other characters are." The showrunners also believed that much of Bran's story wouldn't have been "particularly cinematic," adding: "Rather than being stuck in a cave for a year, we figured it would be interesting to leave him out for a little bit."
King Bran Would Be Better If He Was In Game Of Thrones Season 5
On some level, the decision to have Bran missing from Game of Thrones season 5 is understandable, but with the full picture of his arc it looks a lot worse. If a character is so important they're going to become Westeros' new King at the very end of the show, then there should be enough to do with them in terms of story and character development that means they don't sit out an entire year. That meant far less screen time and development for Bran, and it absolutely factored into his ending. He was a character people didn't fully understand, with too much telling and not enough showing of how he left Bran behind to become the Three-Eyed Raven.
Exactly what the Three-Eyed Raven's powers are and what Bran could see in both past and future wasn't properly explained either, which became frustrating and confusing. For instance, Bran's actions during the Battle of Winterfell, where he seemed to be doing very little, could have been better with more knowledge of his abilities. That could have come from watching him train more, gaining far greater insight into his visions. Watching more of Bran's struggles and progress could have both better explained him and made him a more rounded character audiences were more invested in. Game of Thrones' King Bran would probably still have been divisive, but it at least would've made more sense.