Well, it could be many reasons. Maybe there was a misunderstanding. Some dark magic might have been used to make his friends think he did something bad. Or perhaps a powerful enemy framed him by planting false evidence. It's hard to say exactly without more context from the fanfiction.
One possible event could be a false accusation within the wizarding community. Maybe someone frames Harry for a serious crime, and his so - called friends believe it without really giving him a chance to defend himself. Another event could be a power struggle within Hogwarts or the wizarding world in general, where people see Harry as a threat and turn against him to gain an advantage.
Another possibility is Dumbledore. In some fan - created stories, if Dumbledore was found to be hiding crucial information about Harry's past or destiny for his own purposes, Harry would surely feel betrayed. After all, Harry had put so much trust in Dumbledore as a mentor.
Harry may also get angry. He could lash out at the person who he believes has betrayed him. For instance, if it was Ron, he might shout at him and say things he doesn't really mean in the heat of the moment. This anger would be a result of his deep - seated hurt from the betrayal.
They're popular because it's a twist on the normal Harry Potter story. People like seeing the hero in a different situation, like being betrayed. It adds drama.
Well, in 'harry betrayed by the light fanfiction', it could be that the so - called good guys, who are associated with the light, have their own agendas. Maybe they sacrifice Harry's well - being or safety for the greater good as they perceive it. For example, they might make decisions without his consent that put him in danger, making Harry feel betrayed. It could also be about secrets being kept from him that, when revealed, make him feel like he can't trust those he thought were on his side.
In fanfiction, the 'betrayal by friends' trope often serves to create drama and character development. For Harry, it could be a shattering experience. However, it also opens the door for new alliances, like with Draco. Draco, who might have his own complex reasons, could see this as an opportunity to show a different side of himself to Harry. It could be a journey of redemption for Draco and a path of self - discovery for Harry.
It's difficult to say for certain if there are popular 'harry betrayed fanfiction' stories. Some fanfictions gain popularity based on how well - written and unique their concepts are. Since the idea of Harry betraying someone or something is a departure from the traditional Harry Potter narrative, it might not be as mainstream. But within the fanfiction community, which is full of diverse and creative interpretations, there could very well be some stories that have a following, though they may not be widely known outside of that specific community.
It could imply that in some fan - created stories about Harry (presumably Harry Potter), the character of Harry has been depicted as betraying someone or something. Maybe he betrays his friends' trust, or goes against the values he's supposed to uphold in the fanfiction world.