Please you can share any reasons you think might has been the cause since I’m still not convinced that the bad state of the economy cause this said billionaire to go broke
I don't know if the story you just told is true and if you know any such billionaire, but first, in what currency was this person a billionaire. One can be a billionaire in certain currencies, but still not be considered so wealthy if we compare it with currencies like the U.S. dollar, GBP, Euro, etc.
That being said, billionaires do not keep their money in fiat, the keep it in different investments/assets, they diversify, and most of these assets will be priced in the USD. The chances that all of their assets and businesses will fail or collapse all at once is very slim and so it makes it hard for what you say to happen.
I am sure that we are all billionaires in some currency. For example we are all millionaires in Japanese currency, the rate there is that if you have a car here, then you have a million Yen there. This is why we need to focus on how things could change based on currency. But, if we are talking about even USA, then a person who is going from billionaire to poor would not be something that would be all based on just economy going worse, that would not be a problem at all.
This should be a very troubled thing when you are not careful and that could be the problem. The reality is we are facing something that is probably not true, a lot of "billionaires" in the world right now would make things change all that much more.