Perhaps Viktor was jealous of Ron and Hermione's relationship. In the heat of that jealousy, he might have overstepped boundaries and put Hermione in a threatening situation. Ron, being protective, wouldn't stand for it and thus saved her. For example, Viktor could have tried to force Hermione to go somewhere with him against her will.
Maybe Viktor has been cursed in some way in the fanfiction, and his actions towards Hermione are involuntary. Harry, being observant, picks up on the strange behavior. He may call upon his friends for help, like Ron. Together, they could form a plan. Harry might use his invisibility cloak to get close to Viktor and Hermione without being noticed and then use a powerful stupefy spell to stop Viktor before he can harm Hermione. And then they would figure out how to break the curse on Viktor.
Some writers might be exploring dark or 'what - if' scenarios for shock value. They want to deviate from the normal, positive relationship portrayal to create something edgy.
After Harry saves Hermione, their relationship could evolve in a more complex way. There could be a newfound respect between them. Harry might have a sense of pride in being able to protect her, and Hermione may feel a bit more vulnerable around him. This could lead to some awkwardness at first, but as they work through it, they become closer. They might start spending more time together, not just for school or magic - related things, but also just to be in each other's company. Their friendship could become the cornerstone of their lives, with Harry always being there to protect Hermione and Hermione always being there to support Harry with her knowledge and wisdom.
In fanfiction, the scenario of Draco saving Hermione from Viktor can be quite complex. It might be part of a larger plot where Draco is secretly working against some dark forces that Viktor has unknowingly become involved with. Hermione could be a key target, and Draco, having some inside information, decides to protect her. This could lead to a whole new relationship dynamic between Draco and Hermione, as she now sees him in a different light, and Draco starts to question his own allegiances.
In the fanfic, perhaps there was some deep - seated jealousy in Ron. He might have felt overshadowed by Hermione's intelligence and Harry's fame for a long time, and it all just boiled over in this really wrong way.
Another way is that Ron could call upon the help of his friends or allies. He might send a Patronus to summon other Gryffindors or even some Hogwarts professors. Together, they overpower Viktor and rescue Hermione. Ron's leadership skills and ability to rally support could be crucial in this situation.
One reason could be envy. Hermione is often very good at academics and magic, and Harry and Ron might be envious of her success. For instance, if Hermione always gets top grades in potions class while Harry and Ron struggle, they could lash out at her out of frustration.
One motivation could be that Draco has developed feelings for Hermione. So, when he sees Viktor as a rival for her attention or a threat to her safety, he takes action to save her.
Well, it could be related to Ron's insecurities. He might be insecure about his place in the group with Harry and Hermione. Hermione is always so confident and sure of herself, and Ron might feel that he doesn't measure up. This could translate into aggression as a way of lashing out. Also, perhaps there's some external influence, like a dark magic object that's affecting Ron's mood and behavior towards Hermione.
Well, it could be that in the fanfiction, Hermione travels to Bulgaria for a magical research project. There, she meets Viktor again. They team up to solve a mystery that has been plaguing the Bulgarian wizarding world. As they do so, their relationship deepens and they have a baby. The story could then be about how they protect their child from the dark forces that were involved in the mystery they solved.