It could be that their friends play a role. Harry, for example, might notice that they are both miserable without each other and intervenes. He arranges for them to meet and talk things through. Through this, they see how much they mean to each other and get back together.
One reason could be that they still love each other but just had a misunderstanding before. Once that misunderstanding is cleared up, they naturally get back together.
One great fanfiction could be 'A New Beginning for Ron and Hermione'. It shows their life after the war, how they slowly realize their feelings for each other and start a relationship. It has really sweet moments like their first date in a wizarding café.
There's 'Sooner Than Expected'. In this fic, a series of events at Hogwarts, like a shared adventure in the Forbidden Forest in their third year, makes Ron and Hermione see each other in a new light and they get together earlier. It has a lot of cute moments between them and also stays true to the overall feel of the original series.
One possible plotline could be that after some time apart, they accidentally meet at a magical event. The old feelings start to resurface as they talk about their shared memories at Hogwarts. They realize that the things that drove them apart were minor compared to their deep connection. So they slowly start to rekindle their relationship.
It gives fans a chance to explore a different side of their relationship. In the books, not all aspects of their relationship were fully explored. Fanfiction allows for more in - depth exploration of their feelings, like how they deal with jealousy or family issues together. Also, it lets fans create their own version of a happily - ever - after for the couple. They can write about their married life, having children, and all those things that fans love to imagine.
One common reason is that they still have feelings for each other deep down. Even though they broke up, the love never really went away. Another reason could be that they realized they made a mistake in breaking up. Maybe they overreacted to a small problem.
Perhaps in the fanfiction, Hermione leaves Ron because of his jealousy issues. Ron has shown bouts of jealousy in the original series, and if that continued to be a problem in the fan - created story, it could be a major factor. For example, if Hermione started to gain more recognition in the wizarding community for her intelligence and contributions, and Ron couldn't handle it well. Or it could be that new characters were introduced in the fanfiction, and Hermione developed a stronger connection or friendship with them, which made her re - evaluate her relationship with Ron.
One reason could be that Hermione is a strong - willed character. In fanfiction, Ron might be depicted in a way that undermines her independence. She wants to be seen as her own person, not just as Ron's love interest.
One reason could be for the sake of creating drama. By showing Ron as controlling, it adds tension to the story. Another might be a misinterpretation of his character traits. If an author emphasizes his protective side too much, it could come across as controlling.
One reason could be a divergence from the original character traits. In the original story, Hermione and Ron have a complex relationship with love and friendship. Fanfiction that misrepresents Hermione's feelings towards Ron might go against the essence of her character. Maybe the fanfiction portrays her as hating Ron in a way that doesn't fit with her growth and development in the official series.
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.