Charlie might be a character who has known Hermione for a long time, maybe through some other connections in the wizarding world. He sees Hermione as someone in need of protection from Ron, whether Ron is acting out of his own accord or is being influenced by external forces. In relation to Ron, he is the one who stands against Ron's actions towards Hermione.
In this fanfiction, it could be that Ron is under the control of a powerful wizard who wants to get to Hermione for some reason. Charlie discovers this plot and decides to protect Hermione. He sets up various traps and wards around the place where Hermione is staying. When Ron, being controlled, tries to attack Hermione, Charlie is there to intercept him, engaging in a magical duel if necessary to save Hermione.
In many fanfictions where Ron saves Hermione from Cormac, it often showcases Ron's protective side. Maybe Cormac was being too pushy or overbearing towards Hermione, and Ron steps in. It could be a moment that solidifies their relationship in the fan - made story, showing that Ron truly cares for Hermione and is willing to put himself in a difficult situation to protect her.
Well, in some versions, Ron might use his quick wit and knowledge of Hogwarts' secret passages to outmaneuver Draco. He could lead Hermione to safety through a passage that Draco doesn't know about.
Well, it could be that Lucius uses his powerful influence in the wizarding world. Maybe he intimidates Ron with threats related to his family's status or he uses some dark magic to create a distraction and whisk Hermione away.
Well, it could be that Snape has been secretly observing Ron's erratic behavior towards Hermione. When the situation gets out of hand, he intervenes. He might use his position as a teacher to discipline Ron and in the process, saves Hermione. Snape is a complex character with a lot of power and knowledge, so he could use various means like his occlumency skills to sense the danger Hermione is in and act accordingly.
Ron might use his Weasley family's unique magic items to save Hermione. For example, if he had a special charm from his mother that could repel dark creatures like Greyback. He just needs to activate it at the right moment when Greyback is closing in on Hermione.
In the fanfiction, it could be that Ron is consumed by jealousy or a false belief. This causes him to lash out at Hermione in a way that endangers her. Fred, having a protective streak, especially towards his friends, jumps into action. He might engage Ron in a duel of sorts, not with the intention to harm but to subdue him long enough to break whatever spell or negative emotion has a hold on Ron and thus save Hermione.
One reason could be Snape's sense of justice. Despite his often - cold exterior, he may not tolerate Ron's unjust behavior towards Hermione. Another reason might be that he sees something in Hermione that he values, like her intelligence or her thirst for knowledge, and doesn't want it to be extinguished by Ron's actions.
Well, this concept might seem a bit out of the blue for some fans. But in fanfiction, anything can happen. Hermione leaving Ron for Charlie could be due to a growing admiration for Charlie's work with magical creatures. She might feel a deeper connection with Charlie's more solitary and dedicated nature compared to Ron's sometimes goofy and laid - back attitude.