You shot too high. If you'd gone for a reasonable number, you'd like have gotten and then exceeded it. When I look at the other projects RPG projects I've backed, they've all aimed for around $3k, and met or exceeded that by a large amount. Look at Do

ilgrims of the Flying Temple (target $4k, reached almost 25k) or Bulldogs (target $3k, reached 10k).
There's a psychological effect and a network effect. If people see the goal as readily reachable, they're more likely to contribute, and if you reach the goal early, even more will pledge (assuming the tangible benefits are sufficient).
And the more contributors you have, the more likely you are to have people that contribute to other projects as well, and you'll cross-pollinate, as it were, with your patrons finding new projects to back, and vice-versa.