I think one primary reason is that most American historians who were writing from the 1930s to the 1980s were basically liberal. They honestly believed that Franklin Roosevelt and the New Deal saved the country [in the Great Depression]. They dominated the historical perspective, and they were very dismissive of Coolidge and Andrew Mellon and Harding and anything that happened in the '20s. In some ways, I think they blamed the 1920s for what happened in the 1930s. I think some liberal historians actually blamed Coolidge, even though liberal economists know better than to do that.
What will most surprise readers?
I hope that it would be discovering John Davis. If readers happen to be conservative, I think they would be encouraged in their views. If they're liberal, they might well not change their minds but hopefully would enjoy at least reading about the two candidates.