Many times people will think of an idea based on something that happened in their own life or because it was something that they were interested in. Most of the people won’t do anything about it, but there are a select few who have the resources to do something about it. In this case, the creator decided to make a television series about zombies.
He maybe enjoyed and thought about the zombie apocalypse and thought he should create a show about it. These people are Robert Kirkman, Tony Moore and Charlie Adlard. They wrote a comic book that transformed into The Walking Dead. Then Frank Darabont made the television series out of the comic book. Since then there have been nine seasons.