Seems to me that it's backed by consensus. Bitcoin is no longer a form of currency but a place to park money; since enough people are demanding this store of value, the price naturally stays/goes up. I am not entirely sure how to distinguish it from a fad in all honesty other than staying power, of which it has shown enough to convince me. That and Bitcoin being the pioneer of some pretty solid tech.
it can only survive if it becomes currency - medium of exchange. I don't see how at the moment
As a place to park money it's doomed. Coordinated government crackdown and entire crypto universe will go down to zero overnight
Although I think govenments just will slowly suffocate cryptos in the next 2-3 years