1) It certainly appears that Einstein merely provided mathematical tests for work of Poincare. (Almost everything else he said, did, and wrote was really.. quite silly.). The genius was provided by Maxwell and Poincare. Einstein’s elegance was in his method of communication.
2) The evidence suggests (see Murray) that we obtain a genius in a field because two prior generations of intellectuals concentrate efforts in that field for status seeking reasons. (Mozart).
3) It also appears that a certain rate of wealth creation is necessary over a sustained period of two generations before genius is ‘affordable’ and therefore emerges because a sufficient number of people have the time and resources to specialize in what is essentially non productive labor.
4). We have argued for a few generations now that it appears to take five to seven hundred years for a civilization to ‘cook’ a philosopher. And that civilizations appear to go thru phases that produce different categories of thinkers in each season.
5) These factors suggest a causal relation that other commenters attribute to sheer temporal correlation. That is: it’s very expensive to get enough IQ available and working on intellectual production, over enough generations, that minor insights can accumulate in sufficient numbers that someone from a following generation can synthesize and articulate the common causal relations between those insights and articulate that common causal relation as a new “idea”.
I’d recommend Murray’s tome Human Accomplishment and Joel Mokyr’s various works including The Gifts of Athena.