One possible reason could be that Naruto is afraid of endangering his friends. He has many powerful enemies, and he might think that by staying away from his friends, they won't be targeted. For example, Orochimaru was always after Sasuke, and Naruto might fear that his closeness to Sasuke could put Sasuke in more danger.
Maybe Naruto has some sort of secret mission that requires him to keep his distance. He doesn't want to involve his friends and risk the mission being compromised. He could have been ordered by someone in the village not to let his friends in on what he's doing.
In some fanfictions, Naruto might be hated by his friends due to a misunderstanding. For example, if there's a false rumor spread about him being a traitor. Another reason could be his sudden increase in power that makes his friends jealous. Maybe he accidentally harms one of them during a training session and they hold a grudge.
One possible reason could be that Naruto might be trying to prove his independence. He has grown and wants to show that he can handle things on his own without always relying on Kakashi's guidance.
One possible reason could be that Naruto has seen or experienced something that makes him distrust or fear those around him. Maybe he has discovered a dark secret about the village or his friends that has shaken his beliefs.
One possible reason could be jealousy. Maybe Naruto has been getting more attention from the village elders or teachers because of his potential. His friends, feeling left out or overshadowed, might start to ignore him out of envy.
It creates a lot of tension. His friends will be confused and worried about him. This can lead to them trying to find out what's wrong with Naruto, which drives the plot forward as they search for answers.
One possible reason could be envy. If Naruto suddenly gains a great deal of power or attention in the fanfiction, his friends might feel left out or jealous. Another reason could be a misunderstanding. Maybe Naruto is framed for something he didn't do, and his friends believe the false accusations without giving him a chance to explain. Also, in some fanfiction, a change in Naruto's personality, like becoming overly aggressive or secretive, could lead to his friends growing to dislike him.
One reason could be to seek greater power. In fanfiction, the world outside Konoha might be seen as having more opportunities for growth. They might want to train with different masters or learn unique jutsu not available in Konoha.
Well, sometimes in fanfiction, the author wants to explore the theme of loneliness. So they create a scenario where Naruto's friends abandon him because they are influenced by the village's elders. The elders might spread false rumors about Naruto to maintain their control. His friends, being young and naive, believe these rumors and turn their backs on Naruto, which then leads to Naruto's journey of self - discovery and growth in solitude.
Well, it could be that Naruto's friends are influenced by a dark power. This power could twist their perception of Naruto, making them see him as a threat instead of a friend. Or perhaps there's a prophecy that Naruto is supposed to be the cause of some great disaster, and his friends, in an attempt to prevent it, decide to betray him. It's also possible that a new character enters the story and sows seeds of discord among them, leading to the betrayal.
One reason could be that he's going through some internal struggles. Maybe he has secrets he doesn't want to share. For example, he might be worried about burdening his friends with his own problems.