One reason could be the complex relationship they have in the original series. Fanfic authors often expand on that. Maybe Draco realizes Harry's importance in the fight against the real evil, like Voldemort, and so he becomes protective. It also adds an interesting dynamic to the story, making it more appealing to readers who love exploring different character relationships.
The contrast between Draco and Harry is another reason. Harry is the hero, always in the spotlight, and Draco is from a different world. When Draco becomes protective, it's a sort of reversal. It creates a lot of potential for drama and romance. For example, in many fanfictions, Draco has to go against his family's values to protect Harry, which adds a whole new layer to the story.
In many fanfics, it's about character development. Draco starts to see Harry in a new light, beyond the Gryffindor - Slytherin rivalry. He realizes Harry's vulnerability despite his hero status, which makes him want to protect him. It also adds an interesting dynamic to their romance.
Snape might be protective of Draco in fanfiction because in the original series, Snape has a certain loyalty to the Slytherin house. Draco is a young Slytherin, and Snape could see a bit of his own past self in Draco. Also, Snape was tasked with some difficult and dangerous missions by Voldemort. He might want to protect Draco from getting too deeply involved in Voldemort's dark plans to spare the boy from a similar fate as his own.
Well, in some fanfictions, Snape might be protective of Harry because he sees a lot of Lily in Harry. Lily was Snape's long - loved friend, and Harry is her son. So that connection makes Snape feel an urge to protect Harry from harm, despite their often - rocky relationship in the original story.
In fanfiction, Harry might be protective of Teddy because Teddy is Remus and Tonks' son. Harry has a strong sense of loyalty and he may feel a great responsibility towards Teddy as he lost his parents. Also, Harry has his own experience of growing up without parents, so he doesn't want Teddy to go through any hardships alone.
Well, it's popular because it offers a new and exciting dynamic. Draco and Harry are from different 'worlds' in the original story, being on opposite sides at first. So when Draco is protective in fanfiction, it shows a side of him that we don't see much in the canon. It adds depth to his character and creates a lot of interesting story possibilities, like how he overcomes his previous prejudices to be protective of Harry.
In fanfiction, Harry might be protective of Hermione because of their deep friendship. They've been through so many dangerous adventures together in the original series. Harry values Hermione's intelligence and loyalty, and he doesn't want to see her get hurt. It could also be that in some fanfiction, there are new threats or situations that make him feel the need to be extra protective.
It's popular because it offers a different perspective on their relationship. In the original series, they are sort of enemies. But in fanfiction, seeing Draco be protective of Hermione gives a sense of novelty. People like to explore the idea of characters changing and growing in unexpected ways.
One great fanfiction with this theme is 'The Green-eyed Boy' on FanFiction.net. It shows Harry's protective side towards Draco in a really interesting way, especially during their dangerous adventures at Hogwarts. The author does a great job of building their relationship gradually.
Well, 'The Green-eyed Monster' is another one. Draco's protective nature towards Harry kicks in when there are threats from the Dark forces. It's a slow - burn romance where Draco's actions to keep Harry safe gradually turn into deeper feelings. The author does a great job of building the tension between them.