Maybe Tony believes that Peter is in some kind of danger that May can't protect him from. So, he takes Peter away to keep him safe in a more secure and technologically advanced place that he can provide.
It could also be that Tony has some grand plan in mind related to the future of the Avengers or the safety of the world. He thinks Peter has a crucial role to play and needs to be away from his normal life with May to be prepared for it. For example, he might want to introduce Peter to other superheroes or advanced technology earlier than May would allow.
She may also be worried sick about Peter. She might try to find ways to get Peter back, like contacting other superhero friends of Peter or even going to the media if she has to.
One possible reason could be that Peter might feel like he's a burden to Tony. Maybe he made a big mistake and is afraid of Tony's reaction. For example, if he accidentally endangered the lives of others during a mission while under Tony's supervision.
It could also be due to external pressure. The media or some powerful figures in the fanfiction world might force Tony to stay away from Peter. They could spread false rumors about their relationship or use their influence to separate them for their own gain.
One possible reason could be that Tony Stark is being overly critical of Peter's superhero work. Maybe Peter made a big mistake during a mission, and Tony's harsh words in his attempt to correct Peter made him cry. For example, if Peter accidentally put civilians in danger and Tony scolded him severely.
One possible reason could be jealousy. Maybe Peter has some natural talent or ability that Tony wishes he had, and this makes him mean. For example, if Peter is really good at something like coming up with innovative ideas quickly, and Tony, who is used to being the smartest in the room, feels threatened.
Maybe Peter has some urgent news to share. For example, he might have discovered a new threat to the city or a problem related to one of their projects. He could also be in trouble himself and needs Tony's immediate help.
Tony could be initially shocked. He might not understand why Peter would run away, especially if they had a good relationship before. He'd probably start searching for Peter right away, using all his resources.
Maybe Peter discovers that Tony has been keeping secrets from him that directly affect his life or safety. For example, if Tony has been secretly monitoring Peter without his knowledge, Peter might feel betrayed and cut ties.
One possible reason could be that Tony sees a lot of potential in Peter. In the original story, Peter has great powers and a good heart. The fanfiction might explore different scenarios of their relationship, like a mentor - mentee relationship in more depth. Tony might be interested in how fans envision their interactions and the growth of Peter under his influence.
In the fanfiction world, there could be a prophecy or a pre - determined fate that Tony believes in. He may think that Peter's sacrifice is necessary to fulfill this prophecy and save the world from some greater threat related to the Soyl Stone. He might see it as a selfless act in the long run, even though it seems cruel.