never mind 10 seconds - nobody even got under 10.2 until 1956 - hand timed. The fastest auto was 10.38.
What got the record rush going was the same thing that made the mile record drop 10 seconds in about 10 years. It was not steroids, it was amphetamines introduced in the late 30's and mass marketed after the war. Steroids are what athletes turned to when the IOC started testing for amphetamines - in-competition doping was no longer practical.
If you doubt that it was the speed, not the steroids, look no further than the WR progression you already mentioned. Over the next 18 years it advanced only 0.02 seconds, even though steroid testing didn't begin until 1976 and out-of-competition testing until 1988. Only in 1987 was someone good enough at steroid use to make a big breakthrough. A few years later, his rival Carl Lewis - one of countless sprinters to "accidentally" ingest cold medicine containing ephedra, an amphetamine-like stimulant - managed to approach the nullified record Johnson had set in 1987.
Now watch some old-timer get offended by the implication that there were a lot of elite dopers before 1968 - maybe their own heroes even.
If in-competition use of amphetamines were re-legalized, records would drop by about 1 percent almost immediately. 9.4x, 3.24, 12:30, 26 flat.