I haven't read Huff's book so here's my stab in the dark. Europe has a lot of mainland coastline and the Mediterranean, which favors the formation of many small nation states and trans-Mediterranean trade. Among a large number of diverse and competing states, political, military and social ideas are more likely to be employed somewhere, and if successful, will rise to prominence within the local trade cluster by the process of natural selection.
If you have a large number of independent nation states, many of which import products and ideas from the far East, one of them is likely to put together a new military innovation that gives them an edge in warfare. Since the area sees frequent competition, other nations will quickly come into contact with the new technology and be forced to adopt it, or risk swift decline. A period of rapid innovation in metallurgy, chemistry and navigation (to name only a few) would develop a political culture that values technological development over traditional ideals.
I guess this would increase the demand for scientists/intellectuals and engineers. The total fund allocated by the political elite towards academics either through patronage or universities would increase the number of scientists in Europe. Ease of communication through mail channels and access to wider array of materials, both developed due to the increased volume of trade, would allow more scientists, to do more complicated research and exchange ideas more easily than ever before.
* https://en.wikipedia.org/wiki/Render_unto_Caesar
Certainly the (Catholic) Church had a lot of temporal power, especially in the Papal States, but sovereignty was a bigger thing than in Imperial China or Muslim conquests or caliphs.
Huff also cites the legal framework (amongst other factors): the independence of the judiciary (even from the Church, even though clergy sometimes acted as judges) and a focus on a documented due process acted as checks on runaway power.
The Medieval Origins of the Legal Profession by Brundage is also an interesting read:
* https://www.press.uchicago.edu/ucp/books/book/chicago/M/bo56...
It even covers Roman law, and how it managed to be salvaged (to an extent) and be used as a base for European law, especially starting in the 1200s.
Well, first of all, they had two thousand years autocratic Imperial rule. This was overthrown in 1912, but then came the Japanese invasion, then WW2, then a civil war.
The civil war ended up being won by a somewhat anti-intellectual group of people (the Communists) who had all sort of economic backwards programs (not to mention social upheaval by sending intellectuals to "re-education" camps).
As for the reason why things remained static during the Imperial rule: this was actually the norm for most civilizations. If you look the world in 1600, just before the invention of the telescope, Western Europe, the Ottoman's, the Mughals ruling in India, and Imperial China, weren't too different. The non-Europeans were actually ahead of the Europeans by some metrics.
Once the Scientific Revolution was embraced by the Europeans, and generally rejected by everyone else, the Euros left everyone else in the dust. The real question is: why were the Europeans the only ones to embrace it.
The book Intellectual Curiosity and the Scientific Revolution by Toby Huff explores this question. Highly recommended.