Why did the KKK gain more members in the 1920s?

Their message struck a cord, and membership in the Klan ballooned in the 1920s. By the middle of the decade, estimates for national membership in this secret organization ranged from three million to as high as eight million Klansmen. And membership was not limited to the poor and uneducated on society's fringes. Mainstream, middle-class Americans donned the white robes of the Klan too. Doctors, lawyers and ministers became loyal supporters of the KKK. In Ohio alone their ranks surged to 300,000. Even northeastern states were not immune. In Pennsylvania, membership reached 200,000. The Klan remained a clandestine society, but it was by no means isolated or marginalized.

In the 1920s, the Klan moved in many states to dominate local and state politics. The Klan devised a strategy called the "decade," in which every member of the Klan was responsible for recruiting ten people to vote for Klan candidates in elections. In 1924 the Klan succeeded in engineering the elections of officials from coast to coast, including the mayors of Portland, Maine, and Portland, Oregon. In some states, such as Colorado and Indiana, they placed enough Klansmen in positions of power to effectively control the state government. Known as the "Invisible Empire," the KKK's presence was felt across the country.

Explanation:

the correct answer is history and tradition.