Groups of people can hype themselves into anything. with the advent of digital networks we are literally hit by recurrent storms on digital teacups. unless things get tied back to physical reality those metastable collective mental states can flip back as inexplicably as they have formed.
While a good part of the existing financial system is also based on little else than belief there are some critical parts that aren't: the use of its tools (cash, bank money, credit systems etc) to support real economic interactions. you can't simply switch that system off at will because it is a way for society to keep account of its function. think also of the enforcement of contracts and obligations (eg taxation) - ultimately with the use of physical power.
In other words, for the bitcoin nation its a case of: get real or go to zero.