Disclaimer: I’m worried that this might come across as some attempt to justify or argue for a fascist or cultural supremacist argument — but really I’m wondering if historians have ever pointed to specific cultural or social forces which could arguably have caused this “relative prolificness” (assuming that it really exists).
I know it’s impossible to quantify intellectual and cultural contribution and impact, but surely some type of case can be made for an outsized impact across the board on global culture and thought. Please correct me if I oversimplify with a few examples, but: Einstein started the atomic age, Freud began modern psychology, Marx permanently altered world history via Marxism, Nietzsche began existentialist thought, it seems like Bach, Beethoven and Mozart are the most famous composers in history (and from what I gather, influenced music quite greatly)... There just seems to be a litany of contributions from German-speaking society (Austria, Germany, and the regions that would join into Germany) that literally revolutionized or founded whatever field they were part of.
Basically you're asking, "was German an important country in the 17th-early 20th centuries, from the perspective of our modern, Westernized world." The answer is: yes. But you can come up with similar lists for France and England, if you wanted to, for the same time period. If we were talking from an Asian reference, however, we'd also cite the amazing tremendous still-influential accomplishments of China and Japan, for example.
As for "more" and "more significant" — both of these require really being narrow about what one means by a "contribution" or not. Is Freud more significant than, say, Faraday? It depends on the context you're asking (history of psychology? yes! history of science? maybe not!). There's no way to objectively weigh these.
You could, I suppose, come up with metrics that would let you "measure" things. Here's an arbitrary one: the occurrence of the names of few scientific figures in English books. That produces some sort of ranking. But what sort is it? A somewhat arbitrary measure of Anglophone cultural relevance, for a few randomly picked names? I don't know. This isn't very meaningful. You probably cannot construct too meaningful a scale, though some are probably more meaningful than others (citation counts within science, for example, might be some measure of influence, even if not a perfect or objective one).
Anyway — I don't think anybody doubts that the Germanic-speaking people were one of the "big three" European countries of the 17th-19th centuries. Germany, England, and France had huge influences during this time. Other countries made their marks, too, to be sure. But remember that "influence" is its own funny metric — German music is influential to us, less so to others.
As for "why" — there are conditions that produce lots of cultural and scientific output. Those conditions held for several countries in Europe, and not so much for others. They have held for other parts of the world, too, at other times. (The United States eclipsed Germany in scientific output after WWII, for example — the conditions of which are pretty clear, there! Being bombed to oblivion and split into two countries turns out not satisfy those conditions.) I don't think anybody serious thinks the Germans are uniquely special in this respect.