Do not trash Fiat yourself when it's actually needy, crypto and Fiat must co-exists until the government decide to go digital with Fiat themselves, and Fiat is not trash.
Of course Fiat is not trash.
Fiat is issued by the government and is considered a legal means of payment and is generally used by the wider community in their daily lives. Fiat money makes transactions much easier and more practical, everyone who has Fiat money can buy whatever they want with their money without having to adjust to the seller's wishes for certain goods as barter.
Each country certainly has its own fiat money in accordance with the policies issued by the government of that country, its value is also determined entirely by the government which acts as the manager and guarantor. Its function as a legal medium of exchange in a country makes crypto users willing to exchange their assets into fiat because it can make every transaction easier. As long as the government still places Cryptocurrency as a commodity asset, Fiat will remain the choice of all people in a country as exchange for transactions.