I think the "genius" is kind of a byproduct of transition from faith-centered worldview to knowledge-centered worldview. At the time of mentioned geniuses peopl

I think the "genius" is kind of a byproduct of transition from faith-centered worldview to knowledge-centered worldview. At the time of mentioned geniuses people were just starting to tend away from the faith in god, so the faith in higher powers partially persisted, and labeling people with great achievements as "geniuses" and making it feel like they have something others don't felt like a common sense and intuitive thing to do. So the "genius" might just be a temporary placeholder for the void that left when god was gone. As the void shrank with time, because the religion lost influence and people got better education, the need for people to have something greater then them, i.e. "geniuses" shrank too.