Maybe he just lost interest in it over time. Fanfiction can be a passing fancy, and perhaps he found other hobbies or forms of entertainment that appealed to him more.
It could be that he became too busy with his real life. You know, he might have gotten a new job, started a relationship, or had other important things going on that took up all his time and made it difficult to keep up with fanfiction.
There's also a possibility that he had some negative experiences within the fanfiction community. Maybe he faced criticism for his work or had disagreements with other fans. This could have led to his disillusionment and ultimately his decision to give it up. Another reason could be that he felt like he was spending too much time in a fictional world and wanted to focus more on reality.
Well, it might be that Harry snaps due to his ongoing struggle with Voldemort. After constantly being in a state of fear and having to fight for his life and the lives of his friends, he reaches his limit. He could turn against some of his friends who he feels haven't been fully supportive or understanding. His snapping could lead to a power shift in the wizarding world, as he may start to use his magic in more aggressive and unorthodox ways to protect himself and what he believes in.
He might have more free time to explore other things, like reading classic literature or watching movies.
Another possibility is that the main antagonist could be the wizarding society as a whole. If Harry has been constantly marginalized or misunderstood by the general wizarding population, he could snap and see them as the enemy. Their narrow - minded views and prejudices, like against half - bloods or Muggle - borns, could be what pushes Harry over the edge. He may then try to change or even rebel against the entire wizarding society.
Well, it could be about Harry finally losing his patience with all the constant threats and dark magic. Maybe he decides to take a more aggressive approach against Voldemort and his Death Eaters, instead of always waiting for them to make the first move.
Voldemort would still be a major character. After all, he is Harry's main antagonist. If Harry snaps, it would likely be in relation to his ongoing battle with Voldemort. And the Death Eaters, as Voldemort's followers, would also be involved. They would be on the receiving end of Harry's new, more aggressive stance, and their reactions would shape the story further.
One possible plot could be that Harry discovers some new information about his parents that makes him see Snape in a different light. However, instead of handling it calmly, he snaps because of all the pent - up anger and confusion. For example, if he finds out that Snape had a more complex role in his parents' lives than he thought. His snapping could involve shouting at Snape in front of the whole school, which then sets off a chain reaction of events that slowly changes their relationship from one of enmity to something more like a father - son dynamic, full of misunderstandings and reconciliations.
It could be that Snape teams up with Harry to solve a mystery that is crucial to the wizarding world. During their cooperation, Snape shows his loyalty and intelligence. He may sacrifice some of his own interests for the greater good. Harry witnesses all these and realizes that Snape is not the person he thought he was, thus learning to trust him.
Well, in some fanfictions, Harry might get some pep talk from his friends. For example, Hermione could tell him that Luna is a really nice girl and he should just go for it. This gives him the initial nudge. Then, he might see Luna doing something really cool, like standing up to some bullies or showing off her unique knowledge of magical creatures. That moment could make him think 'She's so amazing, I have to ask her', and finally he just takes a deep breath and does it.
Harry Potter and Severus Snape are the central figures. However, the other Hogwarts professors could also be important. For instance, McGonagall. She might be the one who tries to calm Harry down after he snaps at Snape or she could be the one who encourages Snape to be more understanding towards Harry. Then there are the Death Eaters. If the fanfiction is set in a context where Voldemort is still a threat, the actions of the Death Eaters could impact the relationship between Harry and Snape. They could be the catalysts that force Harry and Snape to work together and ultimately strengthen their father - son - like bond.
Well, it could be that Harry uncovers a conspiracy within the Ministry itself. He might team up with his friends, like Hermione and Ron. They could use their combined skills, Hermione's research and Ron's loyalty. Together, they find out that certain people in the Ministry had motives to frame Sirius. Harry then uses this information to expose the truth and clear Sirius's name. It would involve a lot of investigation, facing some dangerous situations, and outsmarting those who were trying to keep the truth hidden.