It could be that he's been influenced by some sort of dark force without realizing it. In many fanfics, there are often hidden magical elements that can affect a character's behavior. So, this unseen influence might be causing him to be irritable and snap at those around him.
Another possibility is that he's had some sort of personal conflict that has deeply affected him. For example, he might have had an argument with a close friend or found out some disturbing family secrets within the context of the fanfic. These emotional upheavals can lead to him snapping at everyone as a way of lashing out.
One possible reason could be that he's under a great deal of stress. Maybe there are new threats to Berk that he's trying to deal with alone and it's getting to him. Another reason might be personal issues, like if he's having problems with his relationship with Astrid or his father. Or perhaps he's frustrated with the dragons not following his commands as he expects, which makes him lash out at everyone around him.
Another possibility is jealousy. Maybe in the fanfic, Sakura shows more interest in another character, like Sasuke perhaps, and Naruto, who has his own feelings for Sakura, snaps out of envy. It's a common trope in fan - made stories to play with the characters' emotions like this.
Well, communication is key. If his friends sit him down and have an honest conversation with him about his behavior, he might realize how he's been acting. They can share their concerns and let him know how his snapping is affecting them.
One reason could be years of built - up resentment. The villagers have treated Naruto poorly for so long, constantly shunning him and making him feel like an outcast. In fanfiction, this could reach a boiling point where he just snaps. For example, if someone in the village made a particularly cruel comment about his parents, it might be the last straw.
One reason could be stress. Izuku might be under a lot of pressure to keep up with his training and the expectations of being a hero. Class 1A's constant high - energy and sometimes chaotic behavior could push him over the edge. Another reason could be misunderstandings. If they misinterpret his actions or motives, he might snap in frustration. For example, if they think he's showing off when he's actually just trying to help.
One possible reason could be the long - standing emotional neglect Shinji has endured from Gendo. In the Evangelion series, Gendo is often distant and cold towards Shinji, and in fanfiction, this could build up to a point where Shinji snaps.
One reason could be miscommunication. Maybe Sakura said something that Naruto misinterpreted as an insult to his dreams or abilities. For example, if she made a comment about his progress as a ninja in a way that came off as dismissive.
One reason could be a misinformation campaign. Some malicious wizard or witch might have spread false rumors about Harry, making everyone believe that he has done something terrible like being in league with Voldemort again.
In fanfiction, Sasuke might snap at Sakura due to miscommunication. Sakura could be expressing her concern for him in a way that he misinterprets. For instance, if she tells him not to go on a dangerous mission and he thinks she is trying to control him instead of just caring about his safety. Another factor could be the influence of external forces. Maybe there are other characters or events that put him in a bad mood, and Sakura just happens to be there at the wrong time, so he snaps at her.
Well, one reason could be Sakura's constant nagging about Sasuke. Naruto has his own feelings and goals, and if Sakura is always pushing the Sasuke matter in a way that dismisses Naruto's feelings, it might make him snap. For example, if she keeps asking him to bring Sasuke back without considering how hard it is for Naruto.