One reason could be to add a new twist to the story. Fanfic authors might want to make the familiar character of Dumbledore more unpredictable. Another reason might be to explore the idea of power corrupting. Since Dumbledore had a great deal of power, showing him as insane could be a way to show how that power might have affected his mind over time.
There are several reasons. Firstly, some writers may want to subvert the traditional view of Dumbledore. By making him insane, they can create a sense of chaos and make the reader re - evaluate everything they thought they knew about the character. Secondly, it could be a way to explore themes of mental health in the wizarding world. Just because it's a magical place doesn't mean mental illness doesn't exist. And finally, it might just be a creative choice to make a more interesting and unique fanfiction.
Well, in certain Harry Potter fanfiction, Dumbledore can come across as insane. It really depends on the writer's interpretation and the direction they want to take the story. Some might do it for shock value, to create a more edgy or different take on the well - known character. However, the canonical Dumbledore was a highly intelligent and calculating figure, not insane.
One possible reason could be that Harry breaks school rules in the fanfiction. For example, if he ventures into the Forbidden Forest without permission. Dumbledore is strict about the safety of students and such disobedience might lead to punishment.
One possible reason could be a different interpretation of his actions. Maybe in this fanfiction, his use of magic outside of Hogwarts' approved ways is seen more harshly. For example, when he used the Patronus charm to save himself and Dudley in the 'Order of the Phoenix', in this alternate view, it might be considered a criminal act due to the Statute of Secrecy implications.
One possible reason could be a misunderstanding. Maybe Harry overheard something that made him think Dumbledore was planning something against him that he didn't understand. For example, if he heard Dumbledore discussing a dangerous mission for him without his full knowledge.
A possible reason could be jealousy. Maybe Harry sees Dumbledore getting all the praise and respect while he is the one doing all the dangerous work. So, he decides to expose some of Dumbledore's flaws to get some of that attention back.
Maybe Harry finds out that Dumbledore knew more about his family's past than he let on. For instance, if Dumbledore had information about some dark secrets in the Potter family but didn't tell Harry, it could make Harry furious and prompt him to yell. Also, if Dumbledore's actions led to the death or harm of someone Harry cared about, like Sirius, Harry would likely be very angry with him.
One reason could be to explore power imbalances. By making Harry seem like Dumbledore's pet, it shows how much power Dumbledore has over Harry's life and decisions. Another reason might be for a unique storytelling angle. It can create drama and tension, especially if Harry starts to rebel against this 'pet - like' status.
One reason could be a difference in ideology. Harry might have come to believe that Dumbledore's methods, like keeping secrets from him, are not in the best interest of the wizarding world. For example, Dumbledore withheld information about Harry's connection to Voldemort which put Harry in more danger at times. Harry could stand up to him to demand more transparency.
One reason could be a misunderstanding. Maybe Harry discovers some actions of Dumbledore that seem wrong at first glance, like the way he's been handling secrets about Harry's past or Hogwarts' safety. For example, Dumbledore's decision to keep Harry in the dark about certain prophecies might make Harry feel betrayed and lead to a conflict.
One reason could be secrecy. If Harry finds out that Dumbledore has been keeping major secrets from him all along, like about his family or his true role in the wizarding world, he might start to hate him. Another reason could be manipulation. If it seems that Dumbledore has been manipulating Harry's actions for his own gain, that would be a valid cause for hatred in fanfiction.