See:
There Is No Escaping History. Fiat Currency Eventually Fails.
Notice that this is a critique of fiat money -- not a critique of state-issued money under a gold/silver or other standard. Fiat money is a rare occurrence in modern history. (We live in strange times!) As we can see, the examples found by the author are a small number of short periods here and there.
I have my own critique of gold/silver standards, but that's another issue.
Fiat currency is not always fails there is just an incident that fiat currency fails. But not always time they are fails. Fiat currency is the most currency that is use many people or in the whole world. It is first type of currency that use by the people. Crypto currency was built because many people think that fiat currency is not safe, but crypto currency is not totally safe. Digital wallet or crypto wallet is the key to keep your bitcoin safe from the hackers or bad people.