It does seem that quite a few different points in time get credited as when the pendulum swung from the amateur game being supreme in the public's eye, to the professional game taking over supremacy.
In TOMMY'S HONOR, the author seems to believe that after Young Tom Morris's reign the pros replaced the amateurs as being supreme and that afterwards the amateurs where secondary.
One of the shocking aspects of the 1913 US Open is that an amateur beat the pros.
After Bobby Jones retired, it has been said the significance of the amateur in golf plummeted.
Supposedly the 1950s with Billy Joe Patton, Harvey Ward, Venturie, and others was the end of the glory days of amateur golf.