Indian tribes used to trade beads or feathers amongst each other and use those as money because the tribe chief would reliably accept them as a show of homage to his authority (taxes). But should that chief die and be replaced by some dude who don't give two craps about beads or feathers then guess what happens?
Bitcoin is the beads. The USD is the chief.
Not exactly, the beads and feathers were replaced because they weren't useful in as many markets as the USD.
Well let's consider the alternatives... Centralized digital fiat currency won't exist at first. After an economic collapse; nobody will trust the same people who just ripped off the entire world. Banks will be shunned and the population will be fending for itself.
Gold and precious metals, bartering; commodities will come back into play in a big way. Now the biggest problem historically has been piracy of international trade. You can steal wealth from a trader because you know they have a bunch of it on-board the ship. You can raid the ship and physically steal wealth easily.
Bitcoin isn't susceptible in the same way. You can't carry it away.
The advantages of Bitcoin over fiat are amazing, but remember that fiat was also advantageous over gold. Therefore, the advantages of Bitcoin over gold are even more extreme. The issue has always been trust; financial institutions are the problem. Bitcoin will shine when fiat is gone.