If your talking about making into a movie, It's so people could see it how stephanie saw it. Her view became your view. পাঠ করা the book আপনি could imagine many things for Bella but in the movie আপনি see the only face for Bella, Edward, Emmett, etc. Also because the বই were a hit then why wouldn't the চলচ্চিত্র be a hit? People would make a lot of money and those playing the main characters would be known world wide. If your talking about the book it's a simple answer. See Stephanie had a dream which made her sit down and right it. She got engrossed with it and ended up making a whole saga. I mean it can happen. Plus লেখা is a passion to her. Maybe she just wanted to make a new era a ভ্যাম্পায়ার to.