What we call stability of a fiat currency comes from monetary policy, the powers behind it, and the open Market that decides its value. The world takes the Euro and the USD as modern reserve currencies by the Central Banks of several countries. The fractional reserve banking system plus credit and debt have been the primary mechanisms for building trust in fiat currencies' economies. The last century's financial history has shown that this model has been far from perfect but has been the most successful in bringing prosperity to the world.
In the last century-plus, there have been around thirty "Non-Domestic Currency Debt Crisis (typically inflationary deleveragings)," causing millions of people to lose their wealth and transactional value. Recent devaluation hits have occurred in Venezuela, Argentina, Mexico, and Brazil. In 2020, due to the pandemic and the inability of most Governments to adapt, countries worldwide had been jeopardizing their citizens' stores of value, AGAIN.