It could also be due to false accusations. Perhaps an enemy ninja managed to frame them for a heinous crime. Like they were made to look as if they had conspired to assassinate an important figure from another village. This would lead to their banishment as their own villages would want to avoid a full - scale war because of their actions.
Another reason might be related to a forbidden jutsu. If Naruto and Temari were involved in the accidental or even intentional use of a very dangerous and forbidden jutsu that threatened the balance of power among the ninja villages, their villages might decide to banish them to maintain good relations with other villages and to show that they don't tolerate such dangerous behavior.
It could be that Temari accidentally causes a major disaster during a joint mission with Konoha. The Konoha elders, fearing public outcry, banish her. Naruto, who has befriended Temari, doesn't believe she did it on purpose. He then sets out to uncover the real cause of the disaster, which may involve a hidden enemy who framed Temari. Along the way, he has to convince his village that banishing Temari was a wrong decision.
Maybe in the fanfiction, there were some political motives. Hiruzen might have been pressured by other hidden villages. They could have threatened Konoha if Naruto, as the Nine - Tails' jinchuriki, remained in the village. So, to avoid a potential war or conflict, Hiruzen made the difficult decision to banish Naruto. Also, it could be due to a misunderstanding. Naruto might have been in the wrong place at the wrong time during an incident, and Hiruzen misjudged the situation.
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.
One possible reason could be that Naruto discovers some dark family secret that his parents want to keep hidden. For example, if there was a connection between the Uzumaki clan and some forbidden jutsu, and they fear Naruto might be exploited because of it. So they banish him to protect the clan's reputation and his own safety.
One popular 'Naruto x Temari banished' fanfiction might involve them being banished from their respective villages due to some political intrigue. In some fanfics, they end up starting a new life together away from the shinobi world's politics. They could use their skills to build a new community or something similar.
Another reason might be related to Naruto's loyalty being questioned. In fanfiction, there could be a plot where an enemy tricks the guild into believing Naruto has betrayed them. The Fairy Tail guild values loyalty highly, and if they think Naruto has sided with an enemy, they might banish him. For example, if an enemy uses some sort of illusion magic to make it seem like Naruto has attacked a guild member, this could lead to his banishment.
One possible reason could be that she is wrongly accused of a serious crime she didn't commit. For example, if there was a major theft in the village and false evidence was planted against her. Another reason might be that she has some new and powerful abilities that the village elders fear. They may think she could become a threat in the future, so they banish her to protect what they see as the village's stability.
One possible reason could be false accusations of a serious crime. For example, if he was wrongly blamed for a major attack on the village. Another reason might be political intrigue. Some powerful figures in the village might see Naruto as a threat to their power and find a way to banish him to maintain their control.
Well, in fanfiction, his family might banish Naruto due to differences in ideology. Naruto could be advocating for a more inclusive and progressive approach within the family, which goes against the traditional and conservative values of his family. They may see his ideas as a threat to the family's long - established order. Also, if there is a prophecy or some sort of family superstition related to Naruto that they misinterpret, they might banish him to avoid what they think could be a disaster for the family.
Well, perhaps in the fanfiction world, Naruto's parents discover some kind of 'dark power' within him that they fear might be uncontrollable. They think that banishing him is the only way to keep the village safe from this potential threat. This could be a power that is different from the Nine - Tails' chakra and seems extremely dangerous to them.