Well, perhaps it could be that Stiles has faced so many difficult situations in the original story that he just reaches a breaking point and decides to stop caring about the things that used to bother him. Maybe he stops caring about the supernatural threats in his town, and this could lead to a series of events where his friends have to try and bring back the old Stiles.
One possibility is that Stiles has been let down by those he trusted a lot. So, he stops caring as a form of self - protection. In the fanfiction, this could mean he starts to isolate himself from his friends and family. He might not show up for pack meetings or help in battles anymore. His friends would then be on a journey to figure out what went wrong and how to make him care again.
In this 'Stiles stops caring' fanfiction, it could start with a major event like the loss of a close friend. Stiles is so devastated that he shuts down his emotions and stops caring about the world around him. He might start skipping school, ignoring his friends' calls, and generally acting out of character. His friends would be worried and try different ways to reach him. Some might try tough love, while others might be more gentle. They would also have to deal with the consequences of Stiles' new attitude in the face of the town's ongoing supernatural issues.
It could be a new character introduced in the fanfiction. Maybe a powerful witch who has the ability to manipulate emotions. She targets Stiles and makes him stop caring as part of her evil plan to disrupt the balance in the town. Since Stiles is an important part of the group, his change in attitude would cause chaos.
One possible reason could be that Naruto has faced so many betrayals and hardships in the fanfiction. For example, if his friends turned on him for some contrived reasons, it might lead him to stop caring. Another reason could be the constant failure in achieving his goals, like protecting the village but always being undermined by political intrigue within the fan - made story.
Maybe Harry has faced so many traumas and disappointments in the wizarding world that he just decides to distance himself from all the chaos. For example, he might be tired of the constant battles against the Dark Arts and the politics within Hogwarts and the Ministry. He could stop caring about his reputation as 'the Chosen One' and simply want to live a quiet life, away from the spotlight and the expectations.
I'm not sure specifically as there could be many different takes on it. It might be a fanfiction where the character Izuku reaches a point of apathy or stops caring about things he previously held dear, like his dreams of becoming a hero or his relationships. It could be due to some traumatic event or a slow build - up of disappointments in the story's universe.
One possible reason could be that he has been through so much in his original adventures that he's just tired. He might feel like he's constantly being put in new, often contrived, situations in the fanfiction and he simply wants to step away from all the chaos and drama.
Well, it could start with Harry gradually noticing how the fanfiction world is not in line with his own values or experiences. For instance, he might find that the magic system is misrepresented in a way that he can't accept.
One possible reason could be that Naruto has finally realized that Sakura's heart has always been with Sasuke. After years of chasing after her and getting constantly rejected or overlooked, he just gets tired and decides to move on. He might start to focus more on his own personal growth and the other relationships in his life that are more reciprocal.
One possible reason could be that Naruto realizes Sakura's unrequited love for Sasuke. He might feel tired of always being in a one - sided emotional situation with her. Another reason could be that Naruto has his own goals and growth to focus on. His journey to become Hokage and protect the village requires all his attention, leaving little room for his previous feelings for Sakura.
Perhaps Stiles has found something else that he deems more important. It could be a new project, a relationship outside the pack, or a personal goal he wants to pursue. He might think that attending pack meetings is taking away time from this new focus in his life. Also, he could be facing some internal struggles, like self - doubt or a crisis of identity, and he needs some time away from the pack to figure things out.
One possible reason could be that Naruto has faced too many betrayals. Maybe his friends turned on him in the fanfic, which made him lose faith and stop caring.