Final answer:
The author included the hyperbole to emphasize the extraordinary quality of Orpheus' music.
Step-by-step explanation:
The most likely reason that the author included this hyperbole is to emphasize the extraordinary quality of Orpheus' music. By stating that the rivers stopped flowing to hear his music, the author is using exaggeration to convey the idea that Orpheus' music is so beautiful and captivating that even natural elements are affected by it. This hyperbole helps to create a sense of awe and wonder around Orpheus' musical talent.
Learn more about Use of hyperbole in literature