It is impossible for crypto to replace fiat, because the government will not allow that to happen. I think it's better for both to exist,
because it can complement each other. Because from the first crypto was created not to replace fiat, but to eliminating third parties
such as banks. So financial transactions are more efficient and effective.
first of all, I would like to correct you - it is indeed very hard for crypto to replace current fiat, but that is possible in general.
would it be very profitable for everyone? not now
I believe crypto will take its part of economy slowly, but surely in this decade