It could be that after a series of events that make Harry question his own judgment, he submits to Dumbledore's authority. For instance, if there are false prophecies or misinformation floating around that lead Harry astray. Dumbledore, with his greater experience and knowledge, helps Harry see the truth. So Harry decides to submit to Dumbledore in order to get back on the right track and protect Hogwarts and the wizarding world.
In this kind of fanfiction, perhaps Harry, out of fear or some form of coercion, starts to obey Uncle Vernon's every order. Maybe Vernon uses threats about expelling Harry from the house or withholding food to make him submit. This could lead to a very different dynamic in the Dursley household, with Harry being more submissive and not showing his usual defiance.
One possible reason could be a misunderstanding. Maybe Harry overheard something that made him think Dumbledore was planning something against him that he didn't understand. For example, if he heard Dumbledore discussing a dangerous mission for him without his full knowledge.
One possibility could be that Harry, out of a sense of duty or some form of magical coercion, decides to follow his uncle's every order in order to protect his aunt and Dudley from a new magical threat. He might suppress his own desires and instincts to keep them safe.
The main characters would be Harry and Dumbledore. However, the antagonists could also be important. If there is a new dark force in the fanfiction, they would be the ones Harry and Dumbledore are up against. Voldemort's remaining followers could also be part of the equation. Their actions could be what drives Harry to submit to Dumbledore's leadership, as they pose a significant threat to the wizarding world and Harry realizes he needs Dumbledore's guidance to face them.
In such a fanfiction, one possibility could be that Harry Potter defies Dumbledore over the use of certain dark magic items. Maybe Harry believes that Dumbledore is being too cautious and that these items could be used for good in the fight against Voldemort. For example, he might think that the Elder Wand could be harnessed in a different way than Dumbledore anticipates.
I'm not sure if there is a specific 'Harry Potter Dumbledore Stealing Fanfiction' out there. However, if there were, the plot could potentially involve Dumbledore stealing something important like a powerful magical artifact that he believes is necessary to protect Hogwarts or the wizarding world from a great evil, but his actions are misinterpreted by the characters in the fanfiction.
In a fanfiction, Dumbledore might steal out of desperation. Suppose there was a situation where a curse was about to be unleashed on Hogwarts, and the only way to stop it was by stealing a particular ingredient for an antidote from a place where it was not supposed to be taken. Dumbledore, seeing no other option, decides to steal it. His motive here is to save the school and its students, even if it means breaking the rules.
In this fanfiction, it could be about a philosophical difference. Lily Potter might have a different view on how to deal with the threat of Voldemort. Dumbledore is often very strategic and calculating, while Lily could be more impulsive and driven by her emotions and motherly love. So, they could be at odds over how to train Harry or which allies to trust in the fight against the Dark Lord.
One possible plot could be that Dumbledore wants Harry to take on a dangerous but crucial mission earlier than in the original story. He might be desperate because he sees a dark threat approaching faster and believes only Harry has the unique power to stop it.
One possible reason could be that Harry has discovered something about himself or his past that he thinks Dumbledore might not approve of or might try to stop him from exploring further. For example, if he found out some dark magic connection in his family history that he wants to understand on his own without Dumbledore interfering.