In the fanfiction world, there could be a prophecy or some sort of magical connection that compels Draco to rescue Harry. The Dursleys are muggles and their ignorance towards Harry's true nature could be putting Harry in great danger. Draco, being a wizard, senses this and decides to take action. He might also be influenced by a new - found sense of justice that has developed within him over time.
Maybe Draco finally understands that Harry is a victim of circumstances. The Dursleys' treatment of Harry is cruel, and Draco, having grown up in the wizarding world, realizes it's wrong. So he steps in to rescue Harry.
Maybe it was an accident. Like a wrong Floo Powder destination or some kind of misfired spell that landed Draco right at the Dursleys' doorstep just as Harry was there.
Hermione could be one to rescue Harry. She might have discovered some new spell or potion that allows her to bypass the protections around the Dursleys' house and get to Harry. Then she'd use her intelligence and quick thinking to get him out of there safely.
The wizarding world would be in shock. The Malfoys are known for their dislike of the Potters, so Draco saving Harry would go against the family's reputation. It could lead to Draco being ostracized by some in the pure - blood community.
Maybe Percy uses his magic skills to create a distraction. He could conjure up some strange creatures outside the Dursleys' house. The Dursleys, being afraid of all things magical, would be distracted long enough for Percy to sneak in and get Harry out.
Well, it could be that Draco has a change of heart early on. He realizes that the Dursleys are truly awful to Harry. So he uses magic to create distractions. He could make strange things happen around the house that scare the Dursleys so much that they just want Harry to leave. Then Draco could be waiting outside and whisk Harry away to a safer place, like a hidden place in the wizarding world where he has set up a little haven for Harry.
In the fanfic, Snape might use his knowledge of the Dursleys' house layout. He may enter the house unnoticed, find Harry, and then use a Portkey to quickly get them both out of there. He could also have some sort of charm or potion that he uses to counter any magic the Dursleys might have used to keep Harry there, like a spell - breaking potion. And he may have planned the whole rescue very carefully, choosing a time when the Dursleys are least likely to notice, like in the middle of the night.
He could be doing it out of a sense of justice. Despite his family's views, Draco might see that the way the Dursleys treat Harry is wrong and decides to step in.
It could be part of a plot where Draco is given an assignment by someone in the wizarding world to save Harry from the Dursleys. He initially does it for self - serving reasons like getting in good with certain powerful wizards who are concerned about Harry's well - being. But during the process, he actually starts to care about Harry.
Well, one possibility could be that Draco has a change of heart. Maybe he realizes the unfairness of Harry's situation at the Dursleys'. He could use his family's influence or some magic skills he has to get Harry out. For example, he might create a diversion to distract the Dursleys while he sneaks Harry away.
Draco might be initially skeptical. But as Harry goes into details, he could become more empathetic.