I'm not sure that the 'firing' of DeFord Bailey was quite as straightforward as is often implied (I didn't catch what was said about it in the doc). As I recall, the Opry was making changes to its format, and they wanted Bailey to change along with it, which he was, apparently, unwilling or unable to do. It became one of those 'You can't fire me, 'cause I quit!'/'You can't quit, 'cause you're fired!' situations.

Those are my impressions based on things I read and half-remember. I'm no authority on the matter, and am willing to stand corrected.

But, yes, DeFord Bailey was one of the early giants of the harmonica, famous in his day, but largely forgotten outside the world of harmonica-players.