Interesting article I found:
http://earlyradiohistory.us/19209BW.htm
"In May, 1920, Charles A. Stanley, president of the Cosradio Company and operator of amateur radio station 9BW in Wichita, Kansas, was told by his minister, Dr. Clayton B. Wells, that if Stanley's daily broadcasts were going to include Sundays, he should at least be promoting religious activities. So Stanley began broadcasting Dr. Wells' sermons on Sunday evenings. (The Cosradio Company would later operate broadcasting station WEY in 1922-1923)."
Apparently, radio was originally ham radio, which many early ham operators became "commercial broadcasters" when radio went "public" (which is a misnomer since ham radio is public to begin with...)
Here's another:
https://books.google.com/books?id=ZK...=0CDEQ6AEwCDgK
From that last link Aime Semple McPherson began broadcasting in the 20s, got her own license and station in 1924, and was also one of the first preachers on tv.
Could not find when brother Johnson began radio broadcasts.