Earlier quoted context omitted.
"Einstein developed his theory of relatively by simply discarding all the known theories about how physics worked." That's ludicrous nonsense. The primary breakthrough of the theory of relatively was taking what the math had been telling physicists about the universe for years seriously . In hindsight, everything necessary was there before Einstein, it just was very deeply assumed not to be reasonable. Relativity bui…
Yes, he knew them and discarded them. Adam Frank's excellent About Time does a good job of telling the story.
That's the sign of an expert, not a generalist.