Perhaps Naruto is on a quest to understand different summoning animals and their powers. Snakes, being mysterious and having a wide range of abilities, attract his attention. He could also be in a situation where he needs to infiltrate a place that is only accessible with the help of snakes, like a hidden underground lair filled with traps and guarded by creatures that snakes can easily bypass.
One possible reason could be that he is influenced by Orochimaru's techniques. Maybe he discovers some of Orochimaru's old research and figures out how to use snake summoning for his own good. Another reason might be that he is trying to find a new power source to defeat a very powerful enemy that normal jutsu can't handle.
One reason could be to create a unique power - up for Naruto. In fanfiction, authors often want to make their versions of characters stand out. Giving Naruto the ability to summon snakes gives him an edge and a new set of skills to use in battles. It also allows for different strategic approaches compared to his regular abilities.
In some Naruto fanfictions, it's possible for Naruto to summon snakes. Fanfiction often takes creative liberties, so writers might give Naruto this ability for the sake of an interesting plot twist or a new power - up. It allows for different storylines to develop, like Naruto using snake - based jutsus or having a connection to snake - related elements in the Naruto universe that he doesn't have in the original series.
Perhaps it's related to his connection with the Nine - Tailed Fox. In the original Naruto story, he has a strong bond with the Nine - Tailed Fox. In the fanfic, this bond could have evolved in a way that allows him to summon foxes. It could be a manifestation of the latent power within him that he finally manages to tap into and use to summon these fox - like creatures.
Poison or some sort of harmful jutsu effect. Maybe an enemy uses a special poison or a jutsu that slowly weakens Naruto's body. In the fanfic, this could be a new and unique type of attack that he has not encountered before, and his body is not able to withstand it, resulting in fainting.
Perhaps in the fanfic, Hinata has fallen in love with someone else. It could be a new character introduced in the fanfic's universe or someone she has come to know better over time, leading her to reject Naruto.
In some fanfics, there could be a misunderstanding. Suppose Kushina did something that Naruto misinterpreted as harmful to him or his friends. This misinterpretation could lead to his hatred. For example, if Kushina was involved in a mission that Naruto thought put the village at risk, but in reality, she had no choice.
One reason could be a major betrayal. For example, if his friends turned on him, it might shatter his idealistic view and push him towards violence. In fanfic, an author might explore this by having a false accusation against Naruto within the village, causing him to lose faith in the people he once trusted.
One reason could be that the fanfic writer wants to deviate from the original narrative where Naruto gradually gains acceptance. They might want to put him in a situation where he has to struggle more with being unwanted to make the story more interesting. For instance, they could write a scenario where new characters are introduced and they shun Naruto for some reason.
One possible reason could be a misunderstanding. Maybe Naruto misinterprets Hinata's actions or words and distances himself from her. For example, if Hinata is trying to be helpful in a certain situation but Naruto takes it the wrong way. Another reason might be external influence. If there are other characters who try to drive a wedge between them, like some jealous rivals who spread false rumors about Hinata to Naruto. Also, Naruto's own insecurities could play a part. He might feel that he's not good enough for Hinata and decides to let her go on his own accord.
It could also be that Naruto is forced to leave Sakura due to some external threat or danger. For instance, if there is an enemy targeting Naruto and he fears that being around Sakura will put her in harm's way, he would choose to leave to keep her safe. This is in line with Naruto's selfless nature as seen throughout the series.