There is no doubt that 'Game of Thrones' was a watershed in television series, since it concluded six months ago and fans are still talking about it, both for good and bad, and new information continues to emerge about it. its history, like why Jaime chose Cersei in 'Game of Thrones'.
Thanks to the fact that the scripts for the series have been released, we can learn about events that arose throughout the eighth season, which could no longer be treated in depth due to lack of time.
One of them is the strong relationship that exists between Jaime and Brienne of Tarth, which was consummated after the defeat of the Night King and his army of White Walkers, since after the celebration, both characters spent the night together, after which, Jaime decided to return to King's Landing to be at Cersei's side in her most distressing moments.
Many fans thought that Jamie would happily stay with Brienne, she even begs him to stay with him, however, he mentions that he is not the good man she thinks he is and leaves her to go to his sister's side.
Now, we can discover through the scripts (through Insider), that this situation was even more complex and the real reason why Jaime decided to go with Cersei was because he felt guilty for having participated in the battle of Winterfell and having left his sister alone, for which he felt like a traitor.
Fans exploded in fury when they saw what Brienne's character had been reduced to, since she was one of the strongest and toughest characters in the series, which was turned into a woman who runs after a man, which was against everything this character represented in past seasons.
There is no doubt that Jaime had feelings for Brienne, not for nothing did he knight her, when no one else had ever wanted to grant her this position, even though she had a very good position within royalty, so the events after This, they showed that Jaime only got Brienne excited to change her for his sister as soon as he had the opportunity.
However, the script of the series gave a deeper context to this, and it is not that Jaime used Brienne, but that after the two sleep, Jaime stays awake thinking that even though he helped save the world, he felt like a traitor for having abandoned his sister, so this feeling of guilt led him to return to Cersei's side.
In this way, the question of why did Jaime choose Cersei in Game of Thrones is clarified? Since he didn't do it because he didn't have feelings for Brienne or because he was only looking to take advantage of her, but because he couldn't continue living in peace knowing that Cersei could die alone, since her loyalty has always been with her sister.