I'd be fascinated to know more about any actual interaction between the two. Hoover, prior to his presidency during the start of the Depression, had a very good reputation. He had led U.S. European relief work after WWI. He was a squeaky technocrat in today's parlance.
McPherson was probably the most advanced modern evangelist at the time, using radio, pageantry, and all the glitz available to sell her religion, and herself.
It is thought-provoking, even if it is a legend, a good writer could make a heckuva of a novel out of it.
Ali "dig through those files for the smokin' telegram" Infree