It could also be due to jealousy. If Naruto is spending a lot of time with other female characters, Hinata might get angry. Even though she is usually shy and reserved, her love for Naruto could turn into anger if she feels threatened by his closeness to others.
One possible reason could be misrepresentation of her character. In some fanfictions, authors might change her personality to fit a certain plot, like making her overly jealous or mean, which would be out of character for the gentle Hinata. This could make her seem unlikable and thus anger fans who love the original Hinata.
Another reason could be if someone were to slander or disrespect his late mentor, like Iruka or Jiraiya. Naruto holds these people in high regard, and any negative remarks or actions towards them would likely enrage him.
Maybe Sakura makes a decision that endangers herself or the team without consulting Naruto. In the world of Naruto, they are a team, and Naruto values his comrades. If Sakura does something reckless like that, it could make him angry.
It could also be because of Naruto's own insecurities. He might be afraid that Hinata's actions are drawing too much unwanted attention or putting herself in harm's way, and he yells to try and protect her in his own, brash way. He doesn't want to lose her, but doesn't know how to express it other than through yelling.
One event could be if Hinata is forced by her family to make a decision that goes against Naruto's wishes. For example, if her family arranges a marriage for her with someone else, Naruto might be angry at her for not standing up to them. He values freedom and choice, and if he thinks Hinata is giving in too easily, it could make him angry.
One possible reason could be political intrigue within Konoha. Maybe there are certain factions that see Naruto and Hinata as threats to their power. For example, they might be afraid of Naruto's influence due to his status as a hero and Hinata's connection to the Hyuga clan. Another reason could be a misunderstanding. Perhaps some false information is spread about them that makes Konoha turn against them.
One possible reason could be that in the fanfic, Hinata has different personal goals or ambitions that she feels would be compromised if she were to be with Naruto. For example, she might be more focused on her family duties or her own ninja training and career, and she believes that a relationship with Naruto would distract her from those things.
One reason could be that Naruto has grown weary of Sakura's unrequited love for Sasuke. He might feel like she's always focused on Sasuke and doesn't truly see him, Naruto. Another aspect could be that Sakura's constant nagging or her over - emotional outbursts have started to grate on Naruto over time. Maybe he's also tired of having to be the one to always cheer her up when Sasuke - related things go wrong.
Maybe the villagers were being ungrateful for his past sacrifices. Minato was the one who saved the village from the Nine - Tails' attack. If they started to forget his deeds or were misusing the peace he had brought, he would be angry. He might have thought that his efforts were in vain if the villagers didn't uphold the values he fought for.
Another reason could be that Hinata herself undergoes a significant transformation. Maybe she has a spiritual awakening or a change in her life goals that make her realize that her love for Naruto was more of an infatuation based on her younger self's ideals, and as she grows, she no longer feels the same way.