When Harry survived through the killing curse and had supposedly "defeated" the dark lord. All the death eaters were convinced that Harry Potter was the most powerful dark wizard so they went through that misunderstanding and idealised him. That's why Draco wanted to be his friend in the first book because even Lucius and Narcissa were mistaken.
Omg, this is amazing. All these death eaters were legit thinking that an one-year-old was that dark of a wizard. Like he can't even talk and Harry didn't even have wand or have the knowledge to work it.