The reality is murkier. Huge names like Lorentz and Poincare had worked on relativity before Einstein. Gregory and Barrow had proved the fundamental theorem of calculus before Newton, not to mention Leibniz's work.
If you mythologize the past it's easier to look around and wonder why we don't have immortals like Zeus or incredible warriors like Achilles anymore. But the truth is science always proceeds by steps that look small at the time and it's often only in retrospect that things seem amazing and unprecedented.
Semi-relatedly, I used to attend a seminar with a well-known Russian mathematician who would often chime in with Russian/Soviet priority over historical results mentioned by visiting speakers. The cold war created two mathematical cultures that had limited contact. So famous European and American mathematical results from, say the 40s to the 90s often had Soviet versions worked out independently in journals nobody here had ever heard of and written in a language they can't read.
So this is all just a way of saying that empirically, the big kahuna theory of mathematical development seems more fiction than reality. And it should be treated with skepticism when you hear things framed in those terms.
[0] Not that their achievements aren't great. They are all incredible. I just mean they seem more incredible than they are if we forget all the other incredible achievements. Shoulders of giants etc etc.