The existence of bitcoin has nothing to do with the internet, I mean, if bitcoin dies, the internet will not be affected, but if the internet disappears, bitcoin will also disappear. The existence and value of bitcoin is entirely up to us, not anyone else.
Bitcoin transactions without internet are possible, even if your country's government turns off the internet across the country for a few days. There are several ways to make bitcoin transactions without relying on the internet, and you should pay attention to some of the solutions here:
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https://blockstream.com/satellite/The point is bitcoin would not be 0 if the internet did not exist. Some developers will find ways how to do this including doing it by radio network or SMS. So of course the internet is needed for smooth bitcoin transactions, but bitcoin transactions can still be broadcast without internet.