One possible reason could be miscommunication. Maybe Ron said something that Harry misinterpreted, leading to the distrust. For example, if Ron made a joke about Harry's abilities in a time of stress, Harry might take it the wrong way.
It could also be that in the fanfiction, McGonagall has shown some form of bias. Maybe she seems to favor certain students or groups over others, and Harry, being the one who always stands up for fairness, starts to distrust her when he notices this behavior. He might feel that she is not as just as he once thought her to be.
One possible reason could be that Harry discovers some secrets that Dumbledore has been keeping from him. Maybe Dumbledore has been making decisions about Harry's life without his knowledge, like how he was set up to face Voldemort. This lack of transparency might lead Harry to lose trust in him.
Another reason could be outside influence. If there were dark forces trying to drive a wedge between Harry and the Weasleys, they might plant false ideas in Harry's mind. This could make Harry question the Weasleys' loyalty, even though they are truly his friends.
Another reason could be personal insecurities on Harry's part. Harry has been through a lot and might be over - analyzing Ron's behavior. He could be projecting his own fears onto Ron. For example, if Harry is worried about being betrayed again like he was by some people in the past, he might start to doubt Ron even without solid evidence.
Perhaps there were some secrets that Ron was keeping from Harry. In the wizarding world, secrets can be a big deal. If Ron had a secret related to his family or some other important matter and Harry found out about it in a way that made it seem like Ron was hiding something bad, it could lead to Harry not trusting him. Also, Ron's friendship with other characters might make Harry jealous or suspicious. If Ron was getting closer to someone Harry didn't trust, it could spill over and make Harry question Ron's loyalty to him.
One possible reason could be that in the original story, many adults failed him. For example, Dumbledore, while having good intentions, often kept Harry in the dark about crucial matters. In fanfiction, this could be amplified. Harry might have seen adults make decisions that put him and his friends in danger without consulting them. Another reason could be that some adults in the wizarding world have their own political or personal agendas that conflict with what Harry believes is right, so he doesn't trust them.
It might be due to hidden secrets. If there are dark secrets within Konoha that Naruto discovers in the fanfiction, such as a conspiracy that involves some of the higher - ups. This would make him lose trust in the village as a whole.
One possible reason could be that she discovers some of Dumbledore's past actions that seem morally ambiguous. For example, his handling of the situation with Tom Riddle when he was at Hogwarts. Maybe she finds out some details that make her question his judgment.
One possible reason could be past betrayals. Maybe he was let down by his friends or family in the fanfiction's storyline. For example, if someone he trusted shared his secrets with the wrong people, it would make him hesitant to trust anyone again.
It could also be due to a long - standing pattern of behavior. If Ron had been constantly critical or undermining of Harry in the fanfiction, Harry might reach a point where he just can't forgive. Say Ron always made fun of Harry's decisions in front of others, which gradually eroded Harry's trust and patience.