Also this is a “history repeats as a farce” sort of situation. From Arrighi’s “The Long Twentieth Century”:

Why Ming China [1368 to 1644 according to Wikipedia] purposefully abstained from undertaking the kind of “discovery” and conquest of the world into which successive European states soon afterwards began concentrating their energies and resources in fact has a rather simple answer. As Eric Wolf has pointed out, ever since Roman times Asia had been a purveyor of valued goods for the tribute-taking classes of Europe and had thereby exercised a powerful pull on Europe’s precious metals. This structural imbalance of European trade with the East created strong incentives for European governments and businesses to seek ways and means, through trade or conquest, to retrieve the purchasing power that relentlessly drained from West to East. As Charles Davenant was to observe in the seventeenth century, whoever controlled the Asian trade would be in a position to “give law to all the commercial world” (Wolf 1982: 125).

It follows that the expected benefits for Portugal and other European states of discovering and controlling a direct route to the East were incomparably greater than the expected benefits of discovering and controlling a direct route to the West were for the Chinese state. Christopher Columbus stumbled on the Americas because he and his Castillian sponsors had treasure to retrieve in the East. Cheng Ho was not so lucky because there was no treasure to retrieve in the West.