One possible motive could be that Draco wants to annoy Harry. Stealing his glasses is a petty way to get under his skin. It's a simple act of mischief that Draco might think is funny. Another reason could be that Draco is jealous of Harry. By taking something so important as his glasses, he feels like he has some power over Harry.
Maybe it's a form of power play. By taking Harry's glasses, Draco is asserting his dominance. In the wizarding world, status and power are important, and this could be Draco's way of showing that he can take what he wants from Harry, who is often seen as his rival.
Harry could be really angry. He might immediately try to get his glasses back, using some basic spells or just by physically trying to grab them from Draco. He'd be frustrated that Draco is always causing trouble for him.
Well, it could be that Draco steals Harry's glasses as a prank. Maybe he wants to embarrass Harry in front of their classmates. He might hide the glasses in a secret place in Hogwarts, like in an old unused classroom, and Harry has to search for them while dealing with his blurry vision.
One possible reason could be to annoy Harry. Draco is often portrayed as a bully in the Harry Potter series, and stealing Harry's glasses is a way to make his life difficult. It could also be a power play, showing that Draco can take something important from Harry.
Perhaps Draco has developed a sense of respect for Harry over time. He might have seen Harry's courage and determination up close and decided that Harry is worthy of his help. Throwing the wand could be his way of showing that he acknowledges Harry's importance in the fight against the common enemy.
Jealousy could be a big motive. Harry is often the center of attention, and Draco, who is used to being in the spotlight in his own Slytherin circle, might be jealous. So he punishes Harry to try and knock him down a peg or two.
Maybe in some fanfictions, Draco is driven by a sense of self - preservation. He might believe that Harry will eventually turn against him or the Slytherin house. He could think that by killing Harry, he can secure his own place at Hogwarts and in the wizarding community. Additionally, it could be part of a larger plot by Voldemort or his followers. If Draco is forced to join Voldemort's side, he may be given the task of killing Harry to prove his loyalty.
One possible plotline could be that Draco steals Harry's underwear as a prank. He might do it to embarrass Harry in front of their classmates at Hogwarts. Another could be that Draco steals it because he has some strange fascination with Harry and it's a way for him to have something of Harry's. Or perhaps it's part of a dare within the Slytherin group that Draco is a part of.
One possible motive could be to create an emotional shock for Harry. It makes him face a difficult situation and tests his moral compass. Another motive might be to force Draco to reveal some important information, with the torturers knowing that Harry's presence would add extra pressure on Draco.
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.