One possible reason could be a powerful enemy attack. Maybe she was caught in a fight against a much stronger foe who used a deadly jutsu on her. Another reason might be a self - sacrifice. Sakura could be in a situation where she has to give up her life to save her teammates from Team 7.
It could be related to chakra exhaustion. If Sakura overuses her chakra in a very difficult situation, like trying to heal a large number of injured people or in a long - drawn - out battle, it might lead to her death. Her body may not be able to handle the strain, and she slowly starts to fade away as her chakra depletes completely.
Well, it could be about a disease that is slowly taking Sakura's life. Maybe she has some rare illness that the characters in the fanfiction are desperately trying to cure.
One reason could be her importance to the team. Sakura might have some special skills or knowledge that they don't want to lose. So they protect her to ensure the team's overall strength.
One reason could be that they are comparing her to the more physically powerful members like Naruto and Sasuke. Naruto has the Nine - Tails' power and Sasuke has the Sharingan. In comparison, Sakura's initial abilities seem less flashy. Another reason might be that they haven't seen her full potential yet. Maybe she hasn't had a chance to show off her improved combat skills or her advanced medical ninjutsu in front of them.
One possible reason could be that the fanfiction misrepresents Sakura's character. Maybe it portrays her in a way that she would never act in the original context of the series, which makes her seem out of character and thus causes dislike. Another reason might be that the fanfiction focuses too much on other members of Team 7 and sidelines Sakura, making her seem less important or relevant than she actually is in the story.
One reason could be some sort of betrayal he feels. Maybe he discovers a secret that makes him think Team 7 was never truly his team. For example, if he found out that the village leaders had some ulterior motives for forming the team that involved using him.
Perhaps it's a training exercise that gets out of hand. In the world of Naruto, intense training often mimics real battles. If they were sparring and emotions ran high, it could turn into a full - fledged fight. Also, Sakura might be trying to prove herself to Naruto, and Naruto, not understanding her intentions, might respond aggressively.
In some fanfictions, it could be related to the magical core inside Harry. Maybe his magical core was damaged in some way, and over time, it weakened to the point where his body couldn't sustain itself anymore. Since sleep is a vulnerable state, that's when his body finally gives in. Also, it could be part of a complex plot where the author wants to explore the reactions of other characters to Harry's sudden and unexpected death while sleeping. It can create a lot of drama and angst among the remaining characters in the story.
One possible reason could be a vampire attack gone wrong. Maybe a rogue vampire targeted Bella and inflicted a near - fatal wound. Another reason might be related to some sort of dark magic or a curse that was unknowingly placed on her. It could also be due to a self - sacrifice situation where she put herself in harm's way to save someone she loves, like Edward or one of her friends.
One possible reason could be jealousy. Maybe some members of Team 7 are jealous of Naruto's natural talent that he doesn't even realize he has. Another reason might be a misunderstanding. Naruto is often brash and loud, and his teammates could misinterpret this as him being over - confident or show - offish, when in reality he's just trying to prove himself. Also, there could be a pre - existing bias. If some members of Team 7 come from more 'privileged' ninja families, they might look down on Naruto who was an outcast in the village for a long time.
It could be because of a power struggle. Suppose Naruto discovers a new, extremely powerful power within himself, but the village elders or some members of Team 7 are afraid of it. They try to suppress him. Feeling cornered and betrayed first, Naruto could then turn against them. He might believe that he has to protect this new power and use it for what he thinks is right, even if it means going against his old team.