It could also be a way for the writer to express their own dissatisfaction with the original relationship between Sakura and Sasuke. Maybe they felt that Sakura's character was not well - developed in the context of that relationship and decided to create a more 'dramatic' storyline through cheating.
Another possibility is that the writer simply wants to create controversy and get more attention. Cheating is a very polarizing topic, and a fanfiction with such a theme is likely to attract a lot of readers who either strongly oppose or are curiously interested in seeing how the story unfolds.
Some fanfic authors might write it as a form of wish - fulfillment. They might prefer the Naruto - Sakura relationship more than the Sasuke - Sakura one. So, they create a scenario where Sakura turns to Naruto in a romantic way. Additionally, it could be a way to explore the characters' personalities further. For example, how Sasuke would handle being betrayed and how Naruto would deal with being involved in such a situation. It gives a chance to dig deeper into their emotional and moral aspects.
Some writers might want to explore different character traits. They may think that Sasuke has a more complex personality that could lead him to make such a mistake. Also, it could be a way to show Sakura's reaction in a difficult situation and how she might grow or change because of it. In addition, it might be an attempt to break the traditional 'happy ending' mold of their relationship in the original story.
One reason could be to create drama. The idea of a relationship being broken by cheating is full of emotional turmoil which can make for an interesting read. Another reason might be some writers' preference for the Sasuke - Karin dynamic. They might see potential in their relationship that wasn't explored in the original series.
Maybe to explore different character arcs. The writer might want to see how Sakura would develop as a character if she strayed from her loyalty to Sasuke. It could also be a way to introduce new characters or relationships into the Naruto fanfic world.
One reason could be to create drama. The Naruto series has a large and passionate fan base, and a plot like this would shock readers and generate a lot of discussion. Another reason might be that the writer wants to explore different aspects of the characters. Maybe they think Sasuke has a side that could be tempted to cheat, or they want to see how Sakura would handle such a situation.
In a fanfiction where Sakura cheats on Sasuke with Naruto, there could be many consequences. Firstly, it would shatter the trust within Team 7. The camaraderie and unity that they had built over the years would be severely damaged. For Sakura, she might lose the respect of her friends and comrades. In the Naruto world, reputation is important. Naruto himself might be ostracized by some in the village who see him as a home - wrecker, despite his good intentions. And Sasuke could potentially go on a dark path again, seeking revenge or just distancing himself from everyone. Overall, it would create a lot of chaos and emotional upheaval.
Protectiveness. Sasuke has seen a lot of danger in his life. He knows Sakura is a valuable person, both as a friend and as someone he cares about. So his possessiveness could stem from his desire to keep her out of harm's way. He doesn't want any bad guys to get near her.
One possible plot could be Sasuke getting involved with another character due to a misunderstanding or a sense of being drawn to someone who seems to understand a different side of him that he feels Sakura doesn't. For example, if there's a new female character who shares his dark past experiences more directly.
One reason could be the author's desire to create drama. By having such a betrayal, it amps up the emotional turmoil. Another could be to explore different relationship dynamics. Maybe the author wants to see how Naruto would react to such a situation, which is a way of testing the limits of their bond.
Well, one possible plot could be that Sakura, feeling neglected by Sasuke, finds comfort in Itachi's more empathetic nature. Itachi, perhaps, has his own reasons for getting involved with Sakura, like trying to understand the nature of relationships better. However, this would be a very complex and controversial plot as it goes against the established relationships in the original Naruto series.