No, you can pretty much make successful things without that. The Da Vinci Code sold 80 million copies, for example. The Diary of a Wimpy Kid series sold 160 mil

No, you can pretty much make successful things without that. The Da Vinci Code sold 80 million copies, for example. The Diary of a Wimpy Kid series sold 160 million copies over 11 books: James Patterson's Maximum Ride books sold 30 million over 8. Neither of the latter have had anywhere near the media blitz Rowling has had. The goosebumps series in told sold a staggering 400 million copies over its length. Its frustrating because in general these big doorstopper books are usually really bad at kid lit. Harry Potter honestly can't hold a candle to books like Dragonsinger by Anne McCaffrey, or Barbary by Vonda MacIntyre. John Christopher in particular wrote these tiny books that are just master classes in economy; The White Mountains and The Lotos Caves stuck with me for decades. William Sleator managed to do actual intelligent SF for kids, with even some horror to it...something like Interstellar Pig is really surprising even as an adult. Joan Aiken really is a wonderful author too. Its just stuff like potter gets relentlessly pushed and snowballs a lot. There's a lot more of the hive mind instinct that we think, at times.