Lord Voldemort

Context: In a 2001 interview, Rowling said Voldemort was invented as a nemesis for Harry Potter (the protagonist of the novels), and she intentionally did not flesh out Voldemort's backstory at first. "The basic idea [was that Harry] didn't know he was a wizard ... And so then I kind of worked backwards from that position to find out how that could be, that he wouldn't know what he was. ... When he was one year old, the most evil wizard for hundreds and hundreds of years attempted to kill him. He killed Harry's parents, and then he tried to kill Harry--he tried to curse him. ... Harry has to find out, before we find out. And--so--but for some mysterious reason the curse didn't work on Harry. So he's left with this lightning bolt shaped scar on his forehead and the curse rebounded upon the evil wizard, who has been in hiding ever since."  In the second book, Rowling establishes that Voldemort hates non-pure-blood wizards, despite being a half-blood himself. In a 2000 interview with the BBC, Rowling described Voldemort as a self-hating bully: "Well I think it is often the case that the biggest bullies take what they know to be their own defects, as they see it, and they put them right on someone else and then they try and destroy the other and that's what Voldemort does." In the same year, Rowling became more precise about Voldemort. She began to link him to real-life tyrants, describing him as "a raging psychopath, devoid of the normal human responses to other people's suffering". In 2004, though, Rowling said that she did not base Voldemort on any real person. In 2006, Rowling told an interviewer that Voldemort at his core has a human fear: the fear of death. She said: "Voldemort's fear is death, ignominious death. I mean, he regards death itself as ignominious. He thinks that it's a shameful human weakness, as you know. His worst fear is death."  Throughout the series, Rowling establishes that Voldemort is so feared in the wizarding world that it is considered dangerous even to speak his name. Most characters in the novels refer to him as "You-Know-Who" or "He-Who-Must-Not-Be-Named" rather than say his name aloud. In Harry Potter and the Deathly Hallows, a "taboo" spell is placed upon the name, such that Voldemort or his followers may trace anyone who utters it. By this means, his followers eventually find and capture Harry and his friends Ron Weasley and Hermione Granger. In the second book, Rowling reveals that I am Lord Voldemort is an anagram of the character's birth name, Tom Marvolo Riddle. According to the author, Voldemort's name is an invented word. Some literary analysts have considered possible meanings in the name: Philip Nel states that Voldemort is derived from the French for "flight of death", and in a 2002 paper, Nilsen and Nilsen suggest that readers get a "creepy feeling" from the name Voldemort, because of the French word "mort" ("death") within it and that word's association with cognate English words derived from the Latin mors. CANNOTANSWER

Question: Why did Rowling wait to flesh out Voldemort's backstory?
Answer: The basic idea [was that Harry] didn't know he was a wizard ... And so then I kind of worked backwards from that position