Naruto could be tired of the expectations placed on him. Everyone has always assumed he would be Hokage since he was a child. He might want to break free from those expectations and define his own path. He may feel that being Hokage is more about fulfilling others' wishes for him rather than his own true desires. So, he decides he doesn't want to be Hokage in this fanfiction.
Perhaps Naruto feels that the Hokage has been too strict or unfair in dealing with certain situations. Like if the Hokage didn't support Naruto's way of trying to bring peace and unity, which Naruto firmly believes in. This could lead to a growing resentment and eventually hatred.
One possible reason could be the pressure associated with the Hokage title. Naruto has always been in the spotlight and being Hokage comes with a huge burden of responsibility. Maybe in the fanfiction, he resents how it restricts his freedom to just be himself and have adventures like he used to.
One possible reason could be that Naruto has been mistreated by the villagers in Konoha for a long time. Despite his efforts to gain acceptance, if he's constantly faced with rejection or unfair treatment, it might lead to him not caring. For example, when he was a child, many villagers shunned him because he was the host of the Nine - Tails. This continuous negative experience could build up over time and cause him to lose his sense of loyalty to Konoha.
One possible reason could be the fear of losing his loved ones. In the original Naruto story, many ninjas sacrifice a lot, including their lives. Naruto might have seen this and decided he doesn't want to put himself in such a position.
It could be that in this fanfiction, Naruto has been influenced by some false information about the Fourth Hokage. Some villains might have spread lies about the Fourth Hokage's actions, and Naruto, being young and naive in the story, believes those lies and thus starts to hate the Fourth Hokage.
One possible reason could be that he has been living a life apart from his family for so long that he feels alienated. He grew up alone in Konoha, with no knowledge of his family for a large part of his life. So, when suddenly faced with this family in the fanfiction, it's hard for him to accept.
One possible reason could be the overwhelming stress. Being Hokage means handling a lot of political, social and security issues in the village. Naruto might just feel that he can't take it anymore and decides to quit in the fanfiction. For example, dealing with the constant threats from other villages and internal disputes within Konoha can be mentally and physically exhausting.
Maybe he discovers other dreams or goals. He could find that there are other ways to protect the village and his friends that don't require him to be Hokage. He might be more interested in exploring the ninja world, learning new jutsus, or even teaching the younger generation about ninjutsu rather than taking on the political and leadership role of Hokage.
One possible reason could be that their personalities don't mesh well in the context of the fanfic. Naruto might be portrayed as someone who values different qualities in a partner that Hinata doesn't possess. For example, if the fanfic focuses on Naruto's love for adventure and freedom, he may see Hinata as too reserved and home - bound, which could lead to a lack of romantic feelings.
In the fanfic, Naruto could hate the Hokage because of some bad experiences related to past Hokages. Perhaps he discovers some dark secrets about how the Hokage office has made decisions that he doesn't agree with. It might be something like a cover - up of certain events that Naruto believes should have been dealt with more fairly.