"Anyone who clearly sees how, after Socrates, that mystagogue of knowledge, one philosophical school after another, like wave after wave, arose in turn, and how an unimaginable universal greed for knowledge through the full extent of the educated world steered knowledge around on the high seas as the essential task for every person of greater capabilities, a greed which it has been impossible since then completely to expel from scientific knowledge, and how through this universal greed a common net of thinking was cast over the entire earth for the first time (with even glimpses of the rule-bound workings of an entire solar system)—whoever reminds himself of all this, together with that astonishingly high pyramid of contemporary knowledge, cannot deny that in Socrates we see a turning point and vortex of so-called world history." The Birth of Tragedy
It's interesting that Nietzsche uses the word 'universal' -- because I think the thirst for knowledge is just that. And one man's impact can be overstated (although, if you have to overstate the impact of one man, it certainly might as well be Socrates).
One of the things I love about this work is that Nietzsche expends little effort establishing exactly who precipitated which shifts, but instead attaches grand shifts (and poles of meaning) to figures who are iconic of them. (Though as you put it, Socrates is a solid candidate, and it's hard to think of anyone more significant to this shift). It's almost as if this work about the importance of mythos is itself written in a somewhat mythical style. Regarding the idea that the thirst for knowledge is universal, I'm not positive I agree (or rather, that this type of thirst for knowledge, systematic, all-categorizing knowledge, is and always has been inherent to man, rather than conditionally, contextually developed), but it certainly has some strong proponents. You brought this quote from Aristotle to mind, which I received via Daniel N. Robinson's lecture on metaphysics: "ALL men by nature desire to know. An indication of this is the delight we take in our senses; for even apart from their usefulness they are loved for themselves; and above all others the sense of sight. For not only with a view to action, but even when we are not going to do anything, we prefer seeing (one might say) to everything else. The reason is that this, most of all the senses, makes us know and brings to light many differences between things."
I really do think the desire to know is ingrained in us. It may have been effectively stamped out in some people (one of the greatest crimes), but it was there at birth. I know the Greeks agreed, and they were the living embodiment of that desire for many years.
Man's thirst for knowledge is no mystery as his survival depends on his capacity for reasoning. All goal setting and planning depend on acquiring knowledge. Knowledge gathering is in man's nature and a requirement for survival, unless a man chooses to live as an animal.