Why do I think that George Washington Plunkitt was so open about how he made his money?
Probably the best answer is this: The year before his “autobiography” was written, Plunkitt lost his first election in a long time. He had virtually no hope of getting elected to the same position again, and sensed that his political career was coming to an end. So he figured that it was worth the price of this information to become nationally famous.
Of course, the ironic thing is that almost the opposite of what he had intended happened. Riordan was adept at manipulating words, which is a good skill given the right goal. But Riordan’s goal was not what Plunkitt had anticipated. Riordan actually wrote the book for the opposite side from Tammany Hall, the Civil Service Reformers. And Riordan was good at what he did. He turned Plunkitt into the ultimate stereotype for Tammany. In fact, Plunkitt actually lost his next election because he allowed the book to be published.