If the government behind the Fiat currency becomes insolvent, or acquires extensive debt, their currency may be devalued (relative to other Fiat currencies), their ability to borrow money will be affected (lenders will demand higher interest rates because of the risk), and prices will climb as the currency loses value. At present, Venezuela, Argentina, Zimbabwe, and other countries are suffering due to the inflation they are experiencing.
When fiat currency is failing, the citizenry need a mechanism to trade and move money out of the country without fees and taxes; Bitcoin is an obvious choice. As a “peer to peer” unit of value, Bitcoin has minimal fees and a global reach. It is an ideal mechanism to prop up people when their monetary system is in a shambles, and the value of the local fiat currency drops.