Perhaps he's dealing with some sort of trauma. For example, after the many battles he's been through, like the fight against Voldemort, he may be suffering from post - traumatic stress disorder. To cope with this, he isolates himself from others as he doesn't want to burden them or he's just too caught up in his own dark thoughts.
One possible reason could be the burden of his past. Naruto has faced a lot of hardships and the memories might be overwhelming him, making him want to be alone. For example, the loss of his master Jiraiya might have left a deep scar, and he might feel that isolating himself is the only way to deal with that pain.
It could be due to the trauma he has experienced. Losing friends and facing Voldemort multiple times has surely left deep scars. Isolating himself might be his way of dealing with the post - trauma stress. He needs time alone to heal and come to terms with everything that has happened.
One reason could be the shock of the revelation. Harry has always thought his parents were James and Lily. Discovering Snape is his father would be a huge shock, and he might isolate himself to process this new information.
One possible reason could be a misunderstanding. Maybe Naruto overheard something his family said that he misinterpreted as them not loving or believing in him. For example, if he heard them talking about his wild nature or his past mistakes in a way that he took the wrong way.
In the later part of the plot, there could be a turning point. Maybe Harry realizes that his isolation isn't helping him and that he needs his friends. Or perhaps an external threat arises that forces him to come out of his self - imposed isolation. This could lead to a rekindling of his relationships, and they all work together to face the new challenge stronger than ever before.
Well, if Snape were Harry's dad in this fanfiction, Harry's isolation might take on a different tone. He could be more conflicted. Knowing Snape is his father, a man he had such a tumultuous relationship with before, would make him question his own identity. He might be more withdrawn as he tries to come to terms with this new family truth, and his relationships with his friends might become strained as he feels they couldn't possibly understand what he's going through.
One reason could be a reaction to the Ministry of Magic's mismanagement. In the original story, the Ministry often made mistakes and had corrupt elements. In fanfiction, this could lead to Harry becoming an anarchist as a way to oppose such a flawed system.
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.
Well, it could also be a matter of the source platform's policies. For example, if the platform decides to clean up or restructure its content, fanfictions that don't fit the new criteria might be deleted. Maybe they are trying to focus more on official or high - quality 'Harry Potter' - related content, and fanfictions that are not up to par in terms of popularity, relevance, or legality are removed.
One possible reason could be miscommunication. Maybe Ginny feels neglected by Harry because he's so caught up in his own heroic deeds and doesn't pay enough attention to her. So she might seek comfort or excitement elsewhere.