On other hand yes I guess its hard for them to be in that situation since most of them their money is not stored on their local currency. Majority of them either they hide their wealth on Gold,USD and other assets which cannot easy get affected by inflation or crisis happening in their country.
They are Billionaire because they know how to handle their money and for sure they have good financial advisors that give certain good advice on what to do especially if there's serious happening in their country. Also its really hard to ruin their empire especially if they are already establish person or institution.
When the economic situation gets bad, it affects their business and they need to use their spare assets to keep their business running. Therefore, their hoarding of assets in the form of gold, real estate...is irrelevant and will not save them if they do not have any solution to save their businesses.
During times of economic crisis or recession, even corporations and banks can go bankrupt, let alone billionaires who cannot go bankrupt. For example, the Great Recession of 2008 caused the world's fourth largest bank with over 158 years of history, Lehman Brothers to go bankrupt with debts of up to $600 billion. Or in the 2023 crisis, the US also recorded 5 major bank bankruptcies such as First Republic Bank with assets of more than 220 billion, Silicon Valley Bank with 209 billion...
Bankruptcy happens to every business, every billionaire...no matter how big or small.