Big Bill Broonzy, Wikipedia tells us "began in the 1920s when he played country blues to mostly black audiences. Through the ‘30s and ‘40s he successfully navigated a transition in style to a more urban blues sound popular with working class Black audiences. In the 1950s a return to his traditional folk-blues roots made him one of the leading figures of the emerging American folk music revival and an international star. His long and varied career marks him as one of the key figures in the development of blues music in the 20th century."
Broonzy was picked to replace Robert Johnson at the legendary 1938 From Spirituals to Swing , but there was no Big Bill craze similar to that for Johnson. Which is a shame because Bronzy was a very important bluesman and made some very great music. Here's a 1947 performance "Summertime Blues"--not the Eddie Cochran/Who/Blue Cheer rocker. It's very interesting, starting with piano and guitar lines that might been played in the 1930s,then horns enter with lines from swing and jump blues. This was a dominant sound in Chicago and other African-American urban centers. Even the very early Chess Records and Willie Dixon sides were in this vein. Then in 1948, Muddy Waters recorded "I Can't Be Satisfied" and "Rolling Stone" and a blues styles that had been considered out-of-date was again relevant. A preservationist stream keeping country blues alive was created on the white folk circuit, meanwhile Waters went electric and the modern Chicago blues was created.
If you want to learn more about Broonzy, there are over 100 YouTube videos.Bob Riesman has written a highly-regarded biography I Feel So Good: The Life and Times of Big Bill Broonzy Bob Riesman. which has a very nice website, which includes an appreciation by Pete Townsend, Foreword by Peter Guralnick, multimedia, and other features.This seems like a good place to put in a plug for Elijah Wald's Escaping the Delta: Robert Johnson and the Invention of the Blues. While it is focused on Johnson, it is essential to understanding the whole scope of blues and American popular music. Including Broonzy.