One possible reason could be his unruly behavior. Naruto is known to be a bit of a troublemaker in the series, always pulling pranks. In fanfiction, this might be exaggerated, and the orphanage might not be able to handle it anymore. Another reason could be that he's suspected of being involved in something dangerous or illegal, even if he's innocent. For example, if there are strange incidents around the orphanage and Naruto is the easy target to blame because of his reputation.
One possible reason could be his prankster nature. Maybe he played one too many harmless but annoying pranks on the staff or other orphans, and they decided they'd had enough. Another reason might be the fear of the Nine - Tails within him. Even if the people in the orphanage didn't fully understand what it was, they could sense something dangerous about Naruto and wanted to distance themselves from him for safety reasons.
Maybe he was blamed for some trouble he didn't actually cause. For example, if something went missing in the orphanage and the caretakers wrongly thought Naruto took it.
Maybe he violated some important team rules. For example, he might have gone against the orders of the team leader during a crucial mission.
One reason could be copyright issues. The creators or owners of sakura might be worried about the unauthorized use of their intellectual property in fanfiction.
Maybe in the fanfiction, Marshall made a big mistake that endangered the other Paw Patrol members. For example, he might have accidentally set off a chain of disasters during a rescue mission due to his over - enthusiasm and lack of caution.
Naruto's life becomes a lot more difficult. He has to find shelter on his own. He might start sleeping in abandoned buildings or under bridges. He has to scrounge for food, which could lead him to steal at times. His loneliness intensifies as he no longer has even the meager company of the orphanage. He also becomes more distrustful of people, thinking that if the orphanage could reject him, so could anyone else.
Naruto might start to develop his ninja skills earlier. Without the orphanage, he has more freedom to explore and train. He could find hidden training grounds or meet mentors in unexpected places. His determination to prove himself and show that being kicked out was a mistake could fuel his growth as a ninja.
One reason is that some fanfiction authors may lack a deep understanding of Naruto's character. They might write things that are completely contrary to his values and personality just for the sake of creating a 'unique' story. For example, Naruto is known for his positive attitude and strong will, but in some fanfictions, he could be depicted as a negative or spineless character.
One reason could be that some fans are very purist about the original Naruto story. They might feel that fanfiction often distorts the characters or the plot in ways that go against the essence of what Naruto is all about. For example, changing a character's personality completely to fit a romantic or dark and edgy narrative that doesn't align with the source material.
There are several possible reasons. For one, it could be a way to subvert the expectations of the Naruto character. In the original series, he's so pure and full of life. By having him smoke in fanfiction, writers can create a contrast. It might also be used to set a certain mood, like a gritty or more adult - oriented atmosphere. Additionally, it could be a symbol of his rebellion or a sign of him breaking away from the norms of his ninja village. Writers might use it to explore a different side of Naruto that wasn't shown in the original story.