That’s a misunderstanding. CRTs technically don’t have refresh rates, outside of the speed of the beam. Standards were settled on based on power frequencies, but CRTs were equally capable of 75, 80, 85, 120Hz, etc.

Essentially, the speed of the beam determined how many lines you could display, and the more lines you tried to display, the slower the screen was able to refresh. So higher resolutions would have lower max refresh rates. Sure, a monitor could do 120 Hz at 800x600, but at 1600x1200, you could probably only do 60 Hz.