Premise: The Nashville sound originated during the mid 1950s as a subgenre of American country music, replacing the chart dominance of the rough honky tonk music which was most popular in the 1940s and 1950s with "smooth strings and choruses", "sophisticated background vocals" and "smooth tempos". It was an attempt "to revive country sales, which had been devastated by the rise of rock 'n' roll."
Hypothesis:  The rise of rock 'n' roll devastated honky tonk music