Harry could be following a hunch. He might have found some evidence that links Snape to a solution he needs. For example, he could have discovered a note written by his father or mother that mentions Snape's ability to deal with a certain type of dark magic that is now threatening Harry. So, he takes a chance and goes to Snape, hoping against hope that Snape will be willing to help.
One reason could be to study rare magical plants. Australia has a diverse range of flora, and some of it might have magical properties that are not found anywhere else. So, he travels there to learn about these plants and their potential uses in potions or other magical practices.
Perhaps he was on a quest for a rare magical ingredient only found in PT.
One possibility is that Harry has discovered some long - lost connection between them that he thinks can be exploited. Maybe he's found out that Voldemort has some knowledge or ability that is crucial to solving a problem. For instance, if there's a prophecy that only Voldemort can decipher, Harry might approach him for help, despite their long - standing enmity.
Snape might be interested in Harry Potter fanfiction. He has a complex relationship with Harry in the original series. Fanfiction could potentially show different interpretations of their relationship, which might intrigue him as it could offer new perspectives on his own actions and feelings towards Harry.
One reason could be redemption. Harry realizes that Snape has had a very difficult life and has been on the right side all along, despite his harsh exterior. Harry, being the kind - hearted person he is, would want to save Snape to give him a chance at a better life after all the sacrifices he has made for the wizarding world. For example, Snape's love for Harry's mother Lily was so strong that he dedicated his life to protecting Harry, so Harry might feel a sense of indebtedness.
One reason could be the saturation of certain themes. For instance, the trope of Harry hating Snape in fanfiction might be overdone, and it seems like Harry (in the fanfic world) is tired of that one - sided view.
Perhaps in this fanfiction, Snape has proven himself to Harry in some extraordinary way. Maybe he has saved Harry's life multiple times or has shown his true loyalties that were hidden in the original story. It could also be that Snape has some special connection with Harry that makes Harry trust him unconditionally.
In some fanfiction, the plot might be set in a very stressful situation. For example, if the school is under attack and Snape thinks Harry is being reckless and putting everyone in danger. His way of disciplining Harry in that high - stress moment could be a slap, which then drives the story forward as they have to deal with the aftermath of such an action.
It's popular because Snape is such a complex character. His relationship with Harry in the original series is full of tension and mystery. Fanfiction allows writers to explore different aspects of their relationship, like what if they had been friends or if Snape had been more open with Harry from the start.
One reason could be that Harry Potter is the main character of the series. His story arc is central, and Snape is often a complex figure in relation to Harry. Writers might be more interested in exploring how Harry's actions and growth impact Snape's character and vice versa. Also, Harry has a broader range of relationships within the wizarding world that can be intertwined with Snape's story in fanfiction.