Final answer:
John Scopes and associates were motivated to challenge the Butler Act to defend freedom of speech and academic freedom, promote Dayton, Tennessee, and test the validity of a law that symbolized the culture wars between traditional religious values and modern secular views.
Step-by-step explanation:
John Scopes, George Rappleyea, and others agreed to challenge the Tennessee anti-evolution law, known as the Butler Act, for several reasons. The American Civil Liberties Union (ACLU) saw the Butler Act as an infringement of the freedom of speech and sought to challenge it legally. Local town leaders recognized an opportunity to promote their town of Dayton, Tennessee, through the trial. Furthermore, the trial epitomized the culture wars of the early twentieth century, with conservative Christian fundamentalists on one side, and more secular and liberal modernists on the other. Scopes and his associates may have been motivated by a combination of the desire to uphold academic freedom, to defend the principle of separation of church and state, and to partake in a significant legal test case that had the potential to attract nationwide interest.
William Jennings Bryan defended the Tennessee law, in part because he believed the teaching of evolution undermined the values of rural America and posed a threat to traditional beliefs, especially as Darwin's theories were being co-opted by eugenics advocates. During the Scopes Monkey Trial, Scopes was found guilty and fined $100, and the event became a media spectacle that brought to light the tensions between different societal views on science, religion, and the nature of public education.