Maybe the villagers were being ungrateful for his past sacrifices. Minato was the one who saved the village from the Nine - Tails' attack. If they started to forget his deeds or were misusing the peace he had brought, he would be angry. He might have thought that his efforts were in vain if the villagers didn't uphold the values he fought for.
It could also be that the villagers were involved in some sort of political intrigue or corruption that was endangering the village's future. Minato, as a former Hokage, would be angry if he saw the villagers being part of something that could lead to the downfall of the place he had dedicated his life to protect. He would feel betrayed by those he had once protected.
One possible reason could be for the protection of the village in a very extreme and controversial way. Minato might think that Naruto's presence is attracting too much danger and decides to banish him to keep the village safe.
Maybe he misses Naruto a great deal. Fanfiction might offer different scenarios and stories about Naruto that he finds interesting. It could also be that he wants to see how others perceive his son in fictional tales.
One possible reason could be fear. Naruto has the Nine - Tails inside him, and the villagers might be so afraid of the power of the Nine - Tails getting out of control that they decide to take extreme measures. They might see Naruto not as a person but as a potential threat that needs to be eliminated.
One reason could be years of built - up resentment. The villagers have treated Naruto poorly for so long, constantly shunning him and making him feel like an outcast. In fanfiction, this could reach a boiling point where he just snaps. For example, if someone in the village made a particularly cruel comment about his parents, it might be the last straw.
Maybe Naruto has developed new jutsu or techniques that specifically focus on increasing his speed. He's always been innovative in combat. He could have created a special chakra flow method that allows him to move at a much faster rate compared to Minato. It's also possible that he has tapped into some hidden potential within himself that was previously unexplored.
One possible reason could be the way the villagers treated him as a child. They ostracized him because he was the host of the Nine - Tails. He was often alone and looked at with fear and disdain, which could have gradually built up his hatred.
Maybe Sakura makes a decision that endangers herself or the team without consulting Naruto. In the world of Naruto, they are a team, and Naruto values his comrades. If Sakura does something reckless like that, it could make him angry.
In fanfiction, Naruto could snap at Minato due to the pressure he feels. Naruto has his own ideals and goals for the village, and if he feels that Minato's legacy or the way Minato is revered in the village is somehow hindering his own path or the changes he wants to make, he might lash out. He may think that Minato's actions, while heroic in the past, are now holding the village back in a modern context.
One possible reason could be for Naruto's protection. Maybe Minato knew of some great danger that was coming for Naruto and he thought that banishing him would keep him out of harm's way. Another reason might be related to some prophecy or hidden power within Naruto that Minato feared could be misused if Naruto stayed in the village.
One reason could be Boruto's recklessness. In fanfiction, Boruto might engage in dangerous stunts or actions that go against Naruto's teachings. For example, if Boruto were to use a forbidden jutsu without fully understanding the consequences, Naruto would be angry as it not only endangers Boruto but also those around him.