One possible reason could be the trauma he has faced. Harry has endured a great deal of pain, from the loss of his parents to the constant battles and threats in the wizarding world. He might want to escape all that and find peace away from it.
Another reason could be related to his desire for a different future. He has always been in the spotlight in the wizarding world, and he might want to step away from that fame and build a life on his own terms, away from the expectations and chaos of the wizarding world.
One possible reason could be extreme anger. If something really bad happened to his loved ones, like if Voldemort came back in a different way and killed all his friends and family this time, Harry might be driven to the edge and decide to destroy the wizarding world that couldn't protect them.
One possible reason could be that he's tired of the constant danger and politics in the wizarding world. After all he's been through so much. He might just want a normal, quiet life away from magic.
The plot could start with Harry making a firm decision to leave. He might go into hiding in the Muggle world, changing his appearance and identity. Then, the wizarding world would gradually realize his absence and start to search for him, which could lead to a cat - and - mouse chase.
One reason could be that he's tired of the constant danger and battles. After all he's been through, he might just want a normal, peaceful life away from magic. Maybe he wants to start a family in the Muggle world where his kids can grow up without the threat of dark wizards.
Well, in the traditional sense of the wizarding world of Harry Potter, it seems quite out of place. Wizards rely on magic, not mechanical constructs. However, if we consider a fanfiction scenario, anything can happen. Maybe Harry discovers some ancient magic that allows him to combine magic with technology in a way that enables him to build a mech. It could be a mech that uses magic as its power source, with spells inscribed on its parts for various functions.
It could be about Harry Potter achieving ultimate power and ruling the wizarding world. Maybe he overcomes new and even more dangerous dark forces and in the process, he becomes the king. He could make new laws and bring about great changes to Hogwarts and the entire wizarding community.
In some cases, he could be leaving in search of a greater purpose. He might feel that there are things he can learn or achieve outside the wizarding world that will ultimately help the wizarding community more. He may also leave because of some prophetic vision or a feeling that he doesn't belong there anymore, that his path lies elsewhere, away from the familiar magical realm he grew up in.
One reason could be that he values the authenticity of the wizarding world he lived in, and fanfiction often strays from that.
It could be that in the fanfic, Harry Potter discovers some deep - seated secrets about the wizarding world's power structure. Feeling betrayed, he decides to take extreme actions to expose and destroy it. For example, if he finds out that the Ministry of Magic has been using unethical means to control the wizarding population, he might use his influence and magic to bring it all crashing down. He could start by revealing the truth to the public, which could lead to chaos and the destruction of the established order in the wizarding world.
Sure. Although the wizarding world has its own rich literature, there's no reason to think that Harry couldn't be exposed to Matilda fanfiction. Wizards do have some knowledge of the Muggle world, and with the right connections or by accident, Harry could find himself reading it. He might be curious about the different kind of magic, or rather the extraordinary abilities in Matilda's story that are presented in a non - wizarding way.