One possible reason could be that Snape is starting to see Harry in a different light. Maybe he realizes that Harry has been through a lot and has a moment of empathy. It could also be a sign of a deeper, unspoken connection developing between them in the alternate universe of the fanfiction.
Perhaps Snape is under some sort of magical influence that compels him to be more nurturing towards Harry. In fanfiction, all sorts of magical anomalies can be used to drive the plot. Or it could be that Snape is trying to gain Harry's trust for some ulterior motive, like getting information about Voldemort from Harry in a more subtle way.
One possible reason could be that Snape suspects Harry of something. Maybe he thinks Harry is involved in some sort of mischief or is in possession of something he shouldn't have. Snape has always been a bit of a mystery and is often distrustful of Harry, so this action might be his way of getting to the bottom of things.
One possible reason could be punishment. Snape has always had a rather thorny relationship with Harry in the original series. He might see this as a way to assert his authority over Harry. Maybe Harry has done something in the context of the fanfiction, like accidentally messing up Snape's potion ingredients or getting into an area of Snape's house where he wasn't supposed to be.
One possible motive could be Snape's complex relationship with Harry's father. Snape might see Harry as a way to get back at James in some twisted way. He could also be acting out of a sense of duty to the Dark Lord, believing that taking Harry by force is part of some larger plan to gain power or favor.
Maybe Snape suspects Harry of being involved in some sort of dangerous activity related to the Dark Arts. Pressing him to the wall could be a way to force Harry to come clean about his actions or any knowledge he might have. It could also be that Snape is acting out of his own insecurities and pent - up emotions towards Harry, which he has been suppressing for a long time.
One possible reason could be to get her attention in a very forceful way. Snape is often a complex character in fanfiction, and he might be trying to make Hermione listen to him urgently, perhaps about a dangerous situation in Hogwarts that she's not aware of.
Maybe Harry discovers something about his past, perhaps related to his parents, that only Snape can help with. Snape was closely associated with Harry's parents. He might know some secrets or have some information that could help Harry understand a family mystery or some hidden power within him.
One possible reason could be that Snape is still holding a grudge against James Potter, Harry's father. He might take out his long - standing anger on Harry. Another reason could be that Snape is trying to discipline Harry in his own strict way, but it ends up being too harsh and making Harry cry.
It could be that Harry demonstrates a great deal of magical talent in a new and unique way in the fanfiction. Snape, being a Potions master and a powerful wizard himself, would be impressed by such talent. Also, if Harry shows an understanding of something that Snape values deeply, like loyalty or sacrifice, it would make Snape have a positive view of him in the fanfiction.
Maybe Snape was in a really bad mood and Harry happened to be in the wrong place at the wrong time. Snape is often portrayed as a complex character with a lot of pent - up anger, and Harry might have unknowingly triggered it.
It could be a plot device used by the author of the fanfiction. The touch might be used to create tension or an emotional moment between Snape and Harry. It could signify a turning point in their relationship, whether it's the start of a more positive understanding or the heightening of an existing conflict. For example, the touch could make Harry feel uncomfortable and lead to a confrontation later, or it could make him realize that Snape has a more complex side than he initially thought.