The phenomenon of antimicrobial resistance caused by overuse of antibiotics was predicted as early as 1945 by Alexander Fleming who said "The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily under-dose himself and by exposing his microbes to nonlethal quantities of the drug make them resistant."
Source: https://en.wikipedia.org/wiki/Antimicrobial_resistance#History
Obviously quotes from the history section are hardly authoritative, but I just wanted to check that although his prediction was correct, the mechanism that caused it was misunderstood at that time? My own understanding would be that resistance is about random bacteria being resistant and those bacteria thriving because all other bacteria were killed.