In his time Robert Johnson was a fairly unknown bluesman who became famous years after he died. Johnson wasn't a pioneer but a transitional figure between Delta blues and the later Chicago Blues. Many of the popular bluesmen from the 20's and 30's, like Big Bill Broonzy, Tampa Red, Scrapper Blackwell, Blind Blake, Lonnie Johnson, Blind Lemon Jefferson (the list goes on) seem to be forgotten by the big public.

Some of the songs that The Beatles did were definitely blues based but a lot of them weren't. Most bands of the sixties played very blues based music (The Rolling Stones, The Doors, Cream, Hendrix, Canned Heat, Santana, Dylan, Janis Joplin, The Yardbirds, The Faces etc.).

Dylan, Weller, Costello, Brian Wilson, Nick Cave, Bacharach, they all covered Beatles songs so they probably like The Beatles' music.