One possible reason could be that Ron has deep - seated feelings for Hermione that he's not fully aware of yet. In the story, he might be subconsciously drawn to her and thus won't leave her alone.
It could also be that Ron has made a bet or a promise to someone regarding Hermione. He feels obligated to stay close to her all the time in order to keep his word, even if it annoys Hermione at times.
Maybe in the fanfiction's universe, Ron has a mission or a task that is related to Hermione, and he needs to be constantly around her to fulfill it. For example, he could be protecting her from some hidden danger.
The relationship might be full of comical moments. Ron's attempts to stay close to Hermione could result in all sorts of humorous situations, like accidentally ruining her study time or getting in the way of her other plans.
One possible reason could be a misunderstanding. Maybe they misinterpreted something Hermione said or did, and in a fit of anger or confusion, they decided to leave. For example, if Hermione was working on a project alone without consulting them, they might have felt left out and left in a huff.
It could also be related to some sort of family or pure - blood related matter. Draco's family might have some connection to Hermione that he has just discovered, and he's trying to keep her in place to sort out the implications of this connection, which might involve protecting her from other dark forces or just making sure she doesn't interfere with his family's plans.
Well, it might be that the author simply doesn't like the idea of Hermione and Ron in a sexual relationship as it was portrayed in the original. They could be trying to rewrite the relationship in a way that they find more interesting or true to their own interpretation of the characters. For example, Hermione might be too focused on her studies or her own personal growth in the fanfiction to consider a sexual relationship with Ron. Also, the author may be setting up a situation where Ron has to work harder to earn Hermione's romantic affection rather than it being an assumed outcome.
Another reason could be their different views on how to raise their children. Hermione would likely be very strict with studies and following rules, while Ron might want a more laid - back approach. Disagreements over parenting styles can put a great strain on a marriage and could be a factor in their divorce.
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 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.
It could be due to a misunderstanding. Suppose Ron overhears a conversation between Harry and Hermione that he misinterprets completely. He might think they are plotting against him or don't really consider him a true friend. So in a fit of anger and hurt, he decides to betray them.
One possible reason could be that in the fanfiction, Hermione has different career aspirations. She might be so focused on her magical research or her work in the Ministry that she feels marriage would hold her back. For example, she could be on the verge of a major discovery in the field of spell - modification and doesn't want any distractions.
One possible reason could be that their different career paths put a strain on their relationship. Ron might be more focused on his Auror work, often away on dangerous missions, while Hermione is deeply involved in the Ministry's research and reform projects. The long hours and high - stress of their jobs could lead to less time for each other and growing apart.