The Malfoys could save Harry in fanfiction because of a personal debt. Maybe Harry once unknowingly did something that benefited the Malfoys greatly. This could be as simple as preventing a disaster from befalling their family business or saving the life of a family member secretly. When the time comes, the Malfoys feel obliged to return the favor and save Harry from whatever danger he is in. Also, it could be part of a complex plot where the Malfoys are trying to redeem themselves, and saving Harry is a big step in that direction.
Well, the concept of 'Harry Potter Saved by the Malfoys' in fanfiction is really interesting. It plays with the characters' established personalities. The Malfoys are known for their pure - blood supremacist views in the original books. But in fanfiction, the author might create a backstory or a situation where they have a change of heart. For example, perhaps Draco Malfoy realizes the error of his family's ways and decides to save Harry from a great danger. There could be many different interpretations and plotlines in such fanfictions. You could start by looking at the most reviewed or highly rated ones on the fanfiction websites to get a good read.
In some fanfictions, the Malfoys might save Harry because of a magical bond. There could be a spell or a curse that links their fates together. If Harry dies, something terrible will happen to the Malfoys. So they have no choice but to save him. Also, the Malfoys might be influenced by a new ideology. Maybe they meet a wise wizard who makes them see the error of their ways and convinces them that saving Harry is the right thing to do for the greater good of the wizarding world.
One possible plot twist could be that Lucius Malfoy has a secret alliance with Dumbledore all along and saves Harry to fulfill some greater plan against Voldemort. Another could be that Narcissa Malfoy, out of a mother's love for all children (not just her own), decides to protect Harry. Or perhaps Draco Malfoy betrays Voldemort's orders to kill or capture Harry because he has developed an unexpected friendship with Harry during their years at Hogwarts.
In Harry Potter fanfiction, the Malfoys are often portrayed in a more complex and sometimes positive light. Some fanfictions might explore Draco Malfoy's struggle between his family's beliefs and his own emerging sense of right and wrong. He could be shown as having a change of heart, perhaps influenced by his interactions with Harry and his friends. This gives a new dimension to his character that we don't fully see in the original books.
It could also be a part of a plot by the Malfoys to gain influence. They know Harry is a well - known figure in the wizarding world. By calling him and interacting with him, they might hope to improve their public image or gain some political leverage within the wizarding community.
In fanfiction, their relationship can be complex. Sometimes they might be forced to work together against a common dark threat. For example, in some stories, a new dark wizard arises who is more powerful than Voldemort, and both Harry Potter and the Malfoys have to put aside their differences to stop this new evil. It could also involve a change in Draco Malfoy's character, where he starts to see Harry in a different light and they form an uneasy alliance.
In the 'Harry adopted by the Malfoys' fanfiction, one possibility is that Harry would receive a very different kind of magical education. The Malfoys might try to mold him into a Slytherin - like wizard, but Harry's own Gryffindor - like courage would constantly be at odds with that. Also, his relationship with Draco could be very complex, ranging from initial rivalry as they are brought up in the same household to a possible understanding and even friendship later on.
Well, in such a fanfiction, Harry might be given a very different education. The Malfoys could try to indoctrinate him with pure - blood supremacist ideas at first. But as he grows, he might rebel against it. He could also be exposed to a different social circle within the wizarding world. Maybe he would have more interactions with other Slytherin families and this would change how he views things like House rivalries. And his relationship with Dumbledore would be very strained as the Malfoys are not on good terms with Dumbledore.
One example of 'good Malfoys' in fanfiction could be a scenario where Draco Malfoy has a change of heart early on. He might start to question the pure - blood ideology his family has instilled in him. In some fanfictions, he could secretly help Harry Potter and his friends. This could be due to a growing sense of morality within him, seeing the unjust actions of the Death Eaters.