This evolution in rotor design was years in the making.
The Inefficiency of the Modern Rotor
Speed vs. Thrust
This graph shows actual lift/thrust versus calculated maximum lift/thrust that a ideal rotor system should have with 100% efficiency. What is shown are the approximations, the source show's a more accurate depiction . Source: https://collections.lib.utah.edu/dl_files/5d/e4/5de41dbc5c175875bdf296d0600a3ffff3d4d522.pdf (pg. 51)