Perhaps in this fanfiction, there is a power struggle. The Uchiha have some powerful abilities and Naruto, as the main character, might be seen as a threat to their power. In an attempt to protect their own interests, the Uchiha take actions that Naruto interprets as hostile, and in response, he has to take counter - actions which are misconstrued as betrayal.
One possible reason could be a misunderstanding. Maybe Naruto is forced into a situation where he has to take actions that seem like a betrayal to the Uchiha. For example, if there are political forces at play that make Naruto choose between the safety of the village as a whole and the specific interests of the Uchiha clan. Naruto, being a firm believer in the village's unity, might make a choice that the Uchiha perceive as betrayal.
One possible reason could be fear. Naruto is extremely powerful, and some in Konoha might fear that he could one day lose control of his power. Another reason could be political intrigue. There may be certain factions within Konoha that see Naruto as a threat to their power and influence. Also, jealousy might play a part. Naruto has achieved so much and has the love of many, and some might be jealous and thus plot against him.
One possible plot could be that Naruto discovers he has some Uchiha blood in him. This revelation would change his perspective on himself and his place in the ninja world. He might then start to train more intensively to master Uchiha abilities.
Perhaps there was a dark secret about Naruto's origin that was revealed in a way that made others fear him. For example, if it was discovered that he had some connection to a feared enemy or an ancient evil. This could lead to his betrayal as people's fear overrode their previous loyalty to him. Also, jealousy among his peers could be a factor. If Naruto was constantly getting stronger and more popular, some might have become envious and were easily convinced to turn against him.
The Uchiha might initially be filled with anger. Their trust in Naruto, if it was there before, would be completely shattered. They could start to plot revenge against Naruto, believing that he has wronged them. This could lead to a lot of tense moments in the fanfiction as the Uchiha gather their strength and resources.
One possible reason could be a misunderstanding. Maybe some false information was spread in the village that made Konoha believe Naruto had done something wrong. In fanfiction, things can be exaggerated and misinformation can easily lead to a situation of betrayal.
One possible reason could be that she was forced to betray him. Maybe an enemy got to her family and threatened her to turn on Naruto. For example, in the Naruto universe, there are many powerful villains who would stoop to such tactics.
Another reason might be related to a difference in ideology. Kakashi might have a different view on how to achieve peace or protect the village compared to Naruto. This divergence could lead to actions that Naruto interprets as betrayal. For example, Kakashi might believe in a more conservative approach that involves sacrificing some of Naruto's ideals in order to maintain the stability of the village.
It could also be due to outside influence. An enemy might deceive Naruto's team into believing that Naruto has turned against them. The enemy could plant false evidence or use mind - control techniques on the team members, causing them to turn on Naruto without realizing the truth.
In such a fanfiction, one possible reason could be a misunderstanding. Maybe Sarutobi is misled by false information about Naruto. For example, if some villains manage to plant evidence that makes Naruto seem like a traitor. Another reason could be for the so - called 'greater good'. Sarutobi might think that sacrificing Naruto would save the village from a greater threat. However, this would be a very controversial decision as Naruto is the main character and is supposed to be a hero in the original story.
One possible reason could be jealousy. Naruto is very powerful and some in Konoha might be envious. For example, some minor clans might feel that Naruto, as an outsider in a sense, gets too much attention and resources. Another reason could be fear. His Nine - Tails power is so immense that some might fear he could lose control and endanger the village, so they betray him to try and eliminate the 'threat' before it's too late.