One possible reason could be miscommunication. Maybe Kakashi has been involved in some secret missions or decisions that Naruto doesn't understand, leading to a breakdown in trust. For example, if Kakashi made a call during a battle that put Naruto or his friends in danger without fully explaining it to Naruto later.
One possible reason could be past betrayals. Maybe he has been let down by people he thought were friends in the fanfiction world. For example, if someone he trusted shared his secrets which led to him getting into trouble.
Maybe in some fanfictions, the writer portrays Kakashi in a way that Naruto doesn't resonate with. For example, if Kakashi is written to be too strict or distant in a different way than in the original story, Naruto might not like that version of him.
One possible reason could be that Naruto has had some past experiences within the team that made him feel betrayed or let down. Maybe there was a mission where he thought his teammates didn't have his back. Another reason might be that there are secrets among the team members that Naruto has discovered, and these secrets make him question their loyalty. For example, if one of his teammates was hiding a connection to an enemy, Naruto would naturally start to lose trust.
Another reason could be that in this fanfiction, the plot is set in a way that there is a new training system in the village. And this system doesn't involve Kakashi in Naruto's training. There could be new mentors or a completely different approach to training young ninjas like Naruto, which excludes Kakashi from the equation.
His lack of trust could lead to a lot of misunderstandings. For instance, if someone tries to help him but he misinterprets it as a malicious act because of his distrust. This can create a cycle of more distrust as others start to feel frustrated with him.
It could be due to miscommunication. In the fanfiction, perhaps there were misunderstandings within the family. For example, Naruto might have overheard something that made him think his family didn't have his best interests at heart, but in reality, it was all a big mix - up. So, he gradually lost trust in them.
It could also be due to Sasuke's secrecy. If Sasuke is constantly hiding things from Naruto, like his real intentions or new powers he's acquired, Naruto would naturally start to feel that he can't trust him. Trust is built on honesty and openness, and if Sasuke is being cagey, Naruto's trust in him will fade.
It changes the dynamic between Naruto and the village. Since Sarutobi was an important figure in the village, Naruto's distrust can create a rift not just between them but also between Naruto and the traditional village values Sarutobi represented.
One possible reason could be past decisions made by Sarutobi that Naruto didn't agree with. For example, Sarutobi's handling of the Uchiha situation. Naruto, who values friendship and fairness deeply, might have seen this as a sign of Sarutobi's inability to do what's right, thus leading to his distrust.