In a fanfiction with Ron's betrayal, there could be a situation where the magical world turns against Ron. After all, Harry is seen as a hero and Hermione is highly respected. When Ron's betrayal is revealed, the wizarding community might shun him. This could lead to a redemption arc for Ron where he has to prove himself worthy of forgiveness not only to Harry and Hermione but also to the entire wizarding world. He might have to go through great trials and make huge sacrifices to make up for his actions.
In the world of fanfiction, this could be a very dark and interesting plot. It might be that Ron is influenced by some dark magic or some external force that makes him turn against his best friends. Maybe he's jealous of Harry's fame or feels overshadowed by Hermione's intelligence, leading to his betrayal.
In some fanfictions, it might be because of a love triangle gone wrong. Suppose Ron had unrequited feelings for Hermione and thought she favored Harry too much. And Harry, perhaps misinterpreting Hermione's actions in a crucial situation, joined Ron in betraying her. This would be a complex and emotional reason for the betrayal.
Jealousy is a big one. Ron often feels like he's in Harry and Hermione's shadow. He might see their achievements and feel left out or unimportant, which could lead to his betrayal.
Well, Harry might become very bitter. He could turn to other allies like Neville or Luna for support. He might also start to question all of his relationships and become more withdrawn.
Perhaps in the fanfiction, Ron's jealousy gets the better of him. He might be jealous of Hermione's success or her friendships with other characters like Harry or some of her academic peers. His jealousy could manifest in ways that make Hermione feel suffocated or unappreciated, causing her to end the relationship. Also, Ron may have some habits that Hermione can't tolerate anymore. For example, his slacking off on certain responsibilities or not taking things as seriously as she does.
One possibility is that Ron would be heartbroken and might become a bit of a loner for a while. He could focus more on his career at the Ministry or with the Weasley's Wizard Wheezes. As for Hermione and Remus, they might face a lot of backlash from the wizarding community who are used to the Ron - Hermione relationship.
Perhaps Ron was influenced by outside forces. There could have been dark magic or some other characters manipulating him. It's not uncommon in the wizarding world. Some powerful dark wizards might have preyed on Ron's insecurities to make him turn against Harry.
In this kind of fanfiction, it could be that the author wants to explore a different dynamic. Hermione and Ron have a long - built relationship in the original series. Maybe the author feels that Ron and Hermione have a more 'grounded' connection compared to Harry and Hermione. It could also be about showing Ron's growth and how he becomes more worthy in Hermione's eyes over Harry.
Maybe it's because the fanfiction portrays Ron in a way that she doesn't like. In the original story, she has a complex relationship with Ron. If the fanfiction distorts his character too much, it could be off - putting to her.
In some fanfictions, Ron might be depicted as having a controlling influence over Hermione, but this is not a universal portrayal. Fanfiction is a vast and diverse genre, and different authors may explore different relationship dynamics between the characters.