One possible reason could be betrayal. If Naruto discovers that Konoha has been hiding some dark secrets or has betrayed him in some way, like using him without his full knowledge. For example, if they were secretly using his Nine - Tails power for their own gain without his consent, he might decide to cut all ties.
For Sakura, it would be a huge shock. She has always been a part of Konoha and has strong feelings for both Naruto and the village. She might try to convince Naruto to come back, and if she fails, she would be torn between her loyalty to Konoha and her friendship with Naruto.
One possible reason could be that Naruto discovers some dark secrets about the village leadership that go against his values. For example, if he finds out that they have been using underhanded means to maintain power.
One possible motive could be a misunderstanding. Maybe Naruto discovers some false information that makes him believe Konoha has betrayed him. For example, if he's wrongly led to think that the village elders are planning to harm his friends or his sensei. Another motive could be the influence of a powerful and evil entity that has somehow managed to control Naruto's mind. It could use Naruto's strength to achieve its own goal of destroying Konoha.
In fanfiction, Naruto might kill Konoha if he's under some sort of mind control. Maybe an enemy manages to manipulate his thoughts and turn him against the village. Also, if Naruto experiences a great loss because of Konoha's actions or inactions. Say, if his friends are killed due to Konoha's negligence in protecting them, and he blames the village as a whole. Or if he realizes that Konoha's system is so corrupt that it's causing more harm than good to the world.
Maybe Naruto has seen too many unrealistic or out - of - character portrayals of Konoha in the fanfiction. For example, some might make Konoha overly cruel or its people too stupid, which goes against his understanding and love for his village.
In fanfiction, Naruto might snap at Konoha if he feels betrayed by his friends or the village. For example, if they don't support him when he tries to make important changes or if they side with someone who has wronged him. Also, if the village starts to become too controlling or authoritarian in the fan - created story, Naruto, with his free - spirited nature, would likely snap.
One possible reason could be a search for power. The character might feel that Konoha doesn't offer enough resources or training opportunities for them to fully explore the potential of the Rinnegan. They may believe that there are other places in the Naruto world where they can gain more knowledge and power related to their special eye.
One possible reason could be that Naruto is extremely powerful and his skills are needed to protect Konoha from a new and powerful threat. His combat abilities, like his Rasengan and Sage Mode, are crucial for the village's defense.
Naruto might forgive Konoha because he realizes that holding a grudge won't solve anything. He has seen the destruction that hatred can cause, like during the Pain arc. So, he chooses to forgive in order to move forward and bring about positive change. Another reason could be his respect for the previous Hokages and their ideals for Konoha.
One reason could be that the fanfiction might have misrepresented Naruto's character. He's a complex character with strong values, and if the fanfiction twisted those, he'd have enough. For example, if it made him out to be too subservient to Konoha when he's always fought for change within the village.