How did unicorns turn into the pansyes they are today?

I'm asking myself the same thing about vampires. What happened to the terrifying vampires who feasted on blood and shrank away from the dark in fear of bursting into flames? The media has changed it. All it takes is one new book, movie, song, or whatever to fix into people's minds this image. Meyer killed vampires, and who knows what killed unicorns. It doesn't help that most people don't have any prior knowledge about any of these things, so they can't see the glaring errors and changes in these creatures. So because of the media, people now believe that vampires are hot sparkly creatures and unicorns fly over pretty rainbows.