Why did places like India develop things like Vedantism and Buddhism while Greece developed Platonism and Rationalism? If peoples have the same cognitive equipment, why develop different philosophies?
Actually, if you look at the entire range of philosophers in different cultures, many have covered at least parallel territory. As an example, there were many ancient Chinese philosophers (largely unknown in the West) whose work paralleled or anticipated different schools of Western thought. (Bryan W. Van Norden's Taking Back Philosophy does a good job of highlighting the parallels.)
What does vary widely is which philosophies have been embraced by different cultures and why. While it may be impossible to answer this definitively, it at least seems plausible that different cultures have gravitated to philosophies that address questions that are particularly pressing for them.
As an example, in his book Guns, Germs and Steel, ethnogeographer Jared Diamond proposes that China's large, connected land-mass, without natural barriers, made warfare particularly disastrous and unbounded, and led to a society focused around peace, stability, and cultural unity. Given that, Confucianism was an ideal Chinese philosophy. On the other hand, Europe's hide-and-seek geography encouraged the constant formation of little kingdoms, and small, contained wars, and produced societies that embraced more competition-focused philosophies.
Heidegger blames the difference you mention on the loss of the idea of Unity from Western philosophy, a loss he blames on the Greeks after Socrates. This seems reasonable to me. Roman Christianity must later have had a lot to do embedding this profound difference.
With this philosophical element missing from the Western tradition it developed a philosophy within which it has proved impossible to construct a coherent fundamental theory. Meanwhile the Vedantists and the Perennial philosophy carried on regardless grounded on an axiom of Unity and the non-dual nature of Reality.
As far as logic goes the two traditions share the same results but the interpretation placed on them by the Vedantists is off-limits for the scholastic tradition that emerged after Plato and this ensured that the two traditions maintained their distinct identities.
Differences in language, choice of metaphors, style of argumentation and presentation are often philosophically trivial and derived from culture and history. But in the case you mention it's not quite as simple as just a difference between Greek and Indian culture. There is a fundamental philosophical disagreement on how to interpret the result of logic.
For Indian philosophy the Unity of All would be the correct interpretation of metaphysics. For Greek philosophy there isn't one. Thus the only people who claim an understanding of metaphysics endorse the Indian Upanishads and everyone else has to scratch their heads at its incomprehensibility.
At the risk of being a little rude I'll suggest that the distinct difference in this case is mostly to do with how well the respective camps do philosophy.
I also believe that "peoples have the same cognitive equipment" and in the Grand scheme of things, we are all members of one giant human family. However, within our giant human family, there exists-(and has existed), a wide range of thought and intellectual expression.
For example, why is it that the world's major religions-(i.e. Christianity, Judaism, Islam, Hinduism, Zoroastrianism and Buddhism) all originated in the continent of Asia? Christianity, Judaism, Islam and Zoroastrianism originated in the Middle East, whereas Hinduism and Buddhism originated in Nepal and the greater Indian subcontinent. Is there a single, all encompassing answer to this question? The answer is most likely...no. The reasons can vary from diverse geographies and climates, to random historical circumstances, to the commercial wealth of a society, to the political status of a particular country.
And I believe the same can also be said for other landmark ideas and pioneering systems. The intellectual All-Stars of every society throughout History-(and into the present-day), while noted for their originality, novelty and ingenuity, are also, in many ways, products of their civilization and culture. On the one hand, the great Philosophers, Scientists and Mathematicians, have produced unique ways at better understanding the world and the Universe; though on the other hand, these same Philosophers, Scientists and Mathematicians, were also lifelong members of a specific society which had distinct values and particularized visions of reality.
Why did places like India develop things like Vedantism and Buddhism while Greece developed Platonism and Rationalism ...
First, Vedantism is a non-dual philosophy and is akin to the Pythagorean doctrine of the Monad/One. Whilst Rationalism is associated with Greece other places developed similar ideas, for example again in India, we have the secular school of Lokyata.
That different cultures develop similar ideas show that they touch upon some aspect of the truth as the truth is everywhere and at all times the same. The differences arise from different emphases and the different ways that insight, intuition and ideas are expressed by those that think upon them.
If peoples have the same cognitive equipment, why develop different phikosophies.
This is because philosophy is orientated towards truth and though truth is unitary it is many-faceted (and in fact, infinitely so), to us finite creatures, it appears in different guises.
If peoples have the same cognitive equipment, why develop different philosophies?
Philosophies are basically the result of the human mind, which we can categorise as rational. Rationality is essentially logic plus empirical experience. The human capacity for developing articulated languages with unlimited semantics for verbal communication is crucial to explain the development of human civilisations requiring political coordination across a large number of human beings.
Given this context, there are two thing which explain the variability between different regions of the world. First, logic is agnostic about the furniture of reality. It only assumes that something exists. All our inferences therefore can only follow logically from whatever we take the responsibility of assuming as true. We are responsible for our assumptions.
The second point is that our assumptions are mostly a function of our personal experience of reality and it seems that not two humans have exactly the same experience. This largely explains that we can disagree about most things.
So there is variability but there is also uniformity. Europeans tend to have some beliefs in common while Asians may have some other, very different beliefs in common. This we can trace in a large part to language. Verbal communication is the principal means for spreading ideas across a population speaking the same language. Different regions of the world may have different languages so that ideas born in one region will spread easily throughout this region but will more easily fail to cross over to other regions.
Another aspect is the genesis of ideologies. What is plausible is that ideas are accepted in one population when they are perceived by some people as useful. Some people here may be the whole population or particular groups of people. It seems unlikely that any idea spread to very many people if it does not fulfil some useful role. Thus, ideas tend to spread as a function of the particular historical events of the time.
Since regions of the world are by definition relatively isolated from each other, we should expect that possibly very different ideas will prevail in different regions.
The notion of philosophy covers a very large spectrum of systems of ideas, from individual philosophies to massive cultural fixtures like Confucianism. It seems plausible that each philosophy is initiated by one individual thinking things through on his or her own. However, once a philosophy spreads to other people, it is susceptible to modifications brought by different people. Further, the spread of a philosophy should broadly follow the rule governing the spread of ideas, and so a philosophy should be somehow perceived as useful by those who use it and spread it. Thus, all successful philosophies probably are useful to at least some people.
There are also factors that affect equally all regions. For example, the physic of elementary particles is the same everywhere and therefore in all regions of the world. Geographical features are local to each region but everybody can see the Moon and the Sun whatever the region they live in. Thus, some ideas should be able to spread to all regions of the world despite natural and linguistic barriers.
Philosophy is basically related to thoughts. As you know, there are so many factors that affect our thoughts. Nature, environment, atmosphere, climate, food, etc. affect them. All these factors are inter-related also. So we cannot stick to only one of these factors to reach a conclusion. Great ideas related to great philosophies are discovered in solitude.
Food is one of the most important factors mentioned above. 1. Importance of a sattvik diet ( Satvik food ) 2. Sāttvic, Rājasic and Tāmasic food. The effect of different variants in spirituality is seen in philosophy also.
I believe you have noticed the last part in the first link and came to a conclusion.
As a tailpiece you can think of the reason for the different variants in spirituality.