This is not your fault but the title that they choose for that article is completely clickbait because that is not what the article says, the article is just stating that digital currencies are going to take over the world but at no point it says that they are going to replace fiat currencies, fiat currencies are still going to be in place and it is completely possible that governments are going to choose to create their own cryptocurrencies that are centralized.

So decentralized currencies are not going to really replace anything at least according to this prediction, but it doesn't matter we know that a cryptocurrency like bitcoin is going to become a success regardless of what any government thinks.