Your smartassery aside, you haven't justified how geography determined both decisions. I have expressed two "cultural" possibilities, which may be somehow related to China's geography. I'm eager to know how these factors have been not merely influenced, but determined by geography/biology.
China's unity (caused by it's supposed lack of geographical features that would impede trade or conquest; I won't get into that debate, as I really don't know or care much about Chinese geography) gave it the ability to build such a fleet, but also made it much more susceptable to political whims that would destroy it all at once. Europe, OTOH, was fragmented (due to supposedly much larger barriers to trade and conquest) and therefore had many more actors that could build fleets of exploration. It is much less likely that all of them would simultaneously decide to destroy or stop building these fleets.
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