Some writers might want to explore a different side of Naruto. Maybe they are tired of the same old positive - friendship - based stories and want to create a more edgy or dark take. They could be exploring what would happen if Naruto had a falling out with his friends due to some external factor like a power struggle or a betrayal that he wrongly perceives.
One possible reason could be a misunderstanding. Perhaps Naruto misinterprets some of his family's actions or words. Maybe he thinks his family didn't care about him as much as he thought they should. In fanfiction, authors often play with the idea of miscommunication and how it can lead to strong negative emotions like hatred. Also, if there are other characters in the fanfiction who influence Naruto's view of his family, say by spreading false rumors or manipulating him, that could contribute to his hatred.
It can be quite divisive. Some fans might be extremely offended as Naruto is a beloved character known for his positive traits. This type of fanfiction goes against the established character arc and values. It could make some fans angry that someone would distort Naruto's character in such a way.
In some fanfictions, Naruto might use a powerful jutsu he discovers or masters. For example, he could find a forbidden jutsu that has the power to bring the dead back to life. Maybe it's a jutsu that requires a great sacrifice on his part, like giving up some of his own chakra permanently.
In some fanfictions, Naruto might find his mom through a special jutsu. For example, he could discover a hidden scroll that reveals a time - traveling jutsu. Using this jutsu, he travels back to the time when his mom was alive and meets her. Another possibility is that some powerful entity guides him to a secret dimension where his mom is trapped.
It could be that the 'mother love' in the fanfiction goes against Naruto's own ideals or his perception of family. Naruto grew up without his parents, and if the fanfiction presents a mother love that is forced or not in tune with his experiences, he might hate it. He has his own understanding of love and family through his friends and the village, and this fanfiction concept could be a jarring deviation from that.
One way could be through Naruto feeling neglected by his family. Maybe in this fanfiction, his parents were alive but were always too busy with village affairs, leaving Naruto feeling alone and unloved. This could lead to his hatred as he grows up seeing other families being more present for their kids.
One possible reason could be jealousy. Maybe his brother has some special abilities or gets more attention that Naruto feels he should have. For example, if his brother is really good at a certain jutsu and is always praised for it while Naruto struggles, that could lead to resentment.
One possible reason could be that Naruto feels abandoned. His father was not around during his childhood, and he had to face a lot of hardships alone. Growing up without a father figure, he might have developed resentment.
Jiraiya could be important. He was Naruto's mentor and knew Naruto's father well. He might have some stories about Naruto's parents that could add more depth to the meeting. Maybe he could be there to witness the encounter between Naruto and his mom and share his insights.