So basically, people are paying huge amounts of money to get some empty numbers which are then recorded in a public ledger on the internet. If nobody wants to accept these numbers in exchange for dollars, goods or services, they are as useless as a random number that I write on a piece of paper.
This is also applicable for Fiat. IF no one wants to accept dollar, for instance, then dollar is worthless. Fiat gained value then because it is backed with gold, and now no currency is being backed by a precious stone or whatsoever anymore. Fiat just have a value because the majority agreed that it has a value. This goes for Bitcoin too. Bitcoin has a value because the people agreed it has a value. So if Bitcoin, as you say, is just some empty numbers, then fiat is also a bunch of empty worthless numbers.