Randall Collins, in The Sociology of Philosophies, argues that networks, not individual geniuses, make intellectual creativity. High creativity is rare because it is hard to assemble all the right material conditions for a network of intellectuals to have the leisure, the proximity, and the right kind of problem to generate several competing schools of thought.
You might think that one way to solve this problem would be to have patrons take care of all the material concerns to free the intellectuals to think, argue, and write. It turns out, though, that it also takes the right kind of patron, because it is natural for the patron to look askance at any intellectual developments that would undermine that patron's position. This is true whether the patrons are are rich families, religious authorities, or, especially, the state.
The best circumstances for intellectuals come when they are supported by the small gifts of the many, rather than the exclusive, but string-laden patronage of the few. When intellectual institutions are beholden to a powerful sponsor, they turn their brains and their competitive arguments to the politics of keeping and improving their places, rather than the intellectual problem of improving their ideas.