It could also be that he is tired of the false expectations created by fanfiction. In fanfiction, his character might be portrayed in ways that don't match who he really is. He wants to be true to himself and his ninja way, so he gives up fanfiction.
Some fans might be disappointed. Fanfiction often allows them to explore different scenarios with Naruto's character. If he gives it up, it's like closing a door on those creative possibilities.
One reason could be exhaustion. Naruto has been through a lot in the original story. In a fanfic, if he is continuously put through more and more difficult situations without proper breaks, he might just give up out of sheer tiredness.
Sasuke would likely be conflicted. On one hand, he has his own issues with Konoha, but on the other, he might be surprised that Naruto, who was always so loyal, would give up. He could try to understand Naruto's reasons or maybe even join him depending on the situation.
One possible reason could be that he experiences a great loss, like the death of a dear friend. This might shatter his confidence and make him lose his passion for being a ninja.
Another factor could be the nature of his ninja life. It's full of uncertainties and risks. He may worry that if he falls in love, his loved one could become a target for his enemies. Naruto has made many enemies over the years, and he wouldn't want to put someone he loves in danger, so he decides to give up on love.
One possible reason could be a series of misunderstandings. Maybe his family made decisions that he felt were against his principles or dreams, and after repeated attempts to reconcile the differences, he just lost hope. For example, if his family was against his ninja way, which is such a core part of his identity.
It could be that Naruto has a vision of a different kind of life or place where he can truly be at peace. He might meet someone from another village or group who shows him an alternative way of living that is more appealing than staying in Konoha. And so, he gives up on Konoha to pursue this new path.
One reason could be the overwhelming pressure. Being Hokage means shouldering the safety and well - being of the entire village. Naruto might have realized that he can't bear that kind of stress forever. Another factor could be personal sacrifice. He may have seen how being Hokage has cost others in their personal lives and he doesn't want to go through the same. Also, he might have new dreams or goals that are not compatible with the role of Hokage, like exploring the world outside the village more freely.