Moreover, digital currency is more profitable than fiat currency because digital currency cannot be controlled by itself, which makes it stronger.
More profitable than fiat currencies? I don't think fiat currencies are profitable and they are not to gain profits, cryptocurrencies are different because they are volatile because they have limited supplies and more demand which makes them grow in value over time. Cryptocurrencies are more like assets than currencies which is why.
Fiat currency is controlled by the government, which makes it not very profitable, but digital currency cannot be controlled by the government.
I don't the control has a lot to do with that. Fiat currencies in general are not used that way, they don't gain value if people start demanding for more because they are not bought and sold like cryptocurrencies but they are used for trades like you give money to someone to buy a product from them and vice versa.