In some fanfictions, there might be a new magical element or prophecy that makes Harry question Hermione's motives. If the prophecy says something about Hermione being involved in a dark plot, even if it's false, Harry may start to have doubts about her.
It could also be due to a series of unlucky events. Suppose Hermione's well - intentioned plans keep backfiring in a way that makes Harry question her judgment. Like when she tries to solve a problem but ends up making it worse, Harry might start to lose trust.
One reason could be jealousy. In some fanfictions, if Harry has become very famous and powerful, he might think the Weasleys have different motives for being around him, like using his fame for their own gain. So he starts to lose trust in them.
Fanfiction can sometimes be full of wild speculations and ideas that go against the established rules of the wizarding world. Harry Potter knows how things really work in his world, so he wouldn't blindly trust something that contradicts that knowledge.
It could also be due to some actions of McGonagall that seemed suspicious to Harry. Perhaps she made a decision regarding Hogwarts or Harry's safety that Harry didn't fully understand at the time. In the complex world of the wizarding school, decisions are often made with many factors in mind, but Harry might not be aware of all of them, leading to his distrust.
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 a misinterpretation of their relationships. Maybe the author wants to explore a different dynamic where Harry and Hermione bond over Ron's perceived flaws, like his occasional laziness or his insecurities that might come across as annoying to them in this fictional scenario.
Jealousy can also be a factor. Maybe Harry becomes jealous of Hermione's close friendship with another character, or vice versa. This could create tension and ultimately result in a break - up. In some fanfictions, Hermione's intelligence and success might overshadow Harry at times, causing him to feel insecure in the relationship.
Power could be a reason. If there's a chance for Ron and Hermione to gain a great deal of power by turning against Harry, some fanfictions might explore this. For instance, a new dark power might offer them something they've always desired, like the ability to reform the wizarding world in their own image. They might think Harry would oppose this, so they betray him to get what they want.
It's possible that Harry hates it because he has a certain image of Ron and Hermione in his mind. Fanfiction can sometimes create versions of them that are completely different from what he knows. For example, some fanfiction might focus on a love triangle that he doesn't think exists in their real relationship. This divergence from his perception could lead to his dislike.
One reason could be that Hermione is overly worried about Harry's safety. Since he's always in the middle of dangerous situations, she might think controlling his actions can keep him out of harm's way.