Perhaps in this fanfic, Dumbledore steals something from Harry like a powerful magical heirloom. It could be that he wants to keep it away from Voldemort and believes Harry is not yet ready to handle its power. He might be overstepping his bounds, thinking he knows best as he often does in the original series, but this time it's through stealing.
In the 'Dumbledore steals from Harry fanfic', it could be that Dumbledore steals Harry's memories. He might think that some of Harry's memories are too painful or that they hold secrets that could be used against Harry. However, Harry would then be left confused and betrayed, and this could lead to a big conflict between them as Harry tries to figure out what Dumbledore has done and why.
Well, it could be that Dumbledore steals Harry's Invisibility Cloak for some 'greater good' he believes in. Maybe he thinks it's too dangerous for Harry to have at a certain point in time.
There would also be fans who are simply curious. They might want to read the fanfic just to see how the author justifies Dumbledore's actions. Whether it's because of some dark prophecy or a misunderstanding, they would be interested in seeing how the story unfolds and if the author can make this rather controversial concept seem plausible within the magical world of Harry Potter.
One possible plot development could be that Dumbledore gives Snape to Harry as a sort of guide in the wizarding world. Snape, with all his knowledge and experience, could show Harry things that Dumbledore couldn't. This might include some dark arts knowledge that could be used against Voldemort. It could also be a test for both of them. For Snape, to see if he can truly be selfless in helping Harry, and for Harry, to learn to trust Snape despite their past differences.
It could be that Harry finds out about Dumbledore's secrets regarding the Deathly Hallows. If Harry thinks Dumbledore was more interested in the Hallows for his own purposes rather than for the greater good, it might make him hate Dumbledore.
Perhaps Harry has been misled by someone he trusts. They could have filled his head with lies about Dumbledore, making Harry think that Dumbledore is actually a threat. And his motive would then be to protect the wizarding world from what he believes is a hidden danger in Dumbledore.
Maybe Dumbledore discovers some dark secret about Harry's past that he can't handle. It could also be that Dumbledore is trying to protect Harry in a really strange way, by pushing him away from the dangerous wizarding world around Hogwarts.
One possible plot development could be that Harry initially struggles with having Snape under his 'command' in some way. Since they had a very strained relationship in the original series, Harry might be hesitant to trust Snape even if Dumbledore has given him this new role. He could start by trying to figure out Snape's true intentions.
One possible reason could be that Dumbledore believes he is acting in Harry's greater good. Maybe he thinks that by taking certain items from Harry, he can protect them from falling into the wrong hands. For example, if Harry has a powerful magical artifact that Voldemort desires, Dumbledore might steal it to keep it safe.
In a 'Harry framed Dumbledore' fanfic, a motive could be revenge. Suppose Dumbledore made a decision that Harry thought was wrong and cost someone Harry loved dearly. Harry could then be driven by revenge to frame him. Also, it could be a case of Harry being under the influence of a dark force. The dark force might convince Harry that Dumbledore is a threat and needs to be removed from power, leading Harry to frame him.
One possible reason could be if Harry were to break a major school rule in the fanfic, like using dark magic without proper authorization. Dumbledore is a strict adherent to the rules of Hogwarts and would likely punish such behavior.
Perhaps in the fanfic, Harry discovers that Dumbledore has been manipulating him all along. Dumbledore has always been a very complex character with many secrets. If Harry were to find out that Dumbledore was using him as a pawn in a much larger and dangerous game, his anger could lead him to punch Dumbledore. This would completely change the dynamic between them and open up a whole new set of storylines and character developments.