It's clearly a bubble, the value of individual coins is speculative and incredibly volatile, and it's one that carries enormous regulatory risk from governments that see the value of the tech but would much prefer they be in the driver seat.
Fedcoins offer the government both complete control and maximum flexibility over the money supply, and gives them the ability to control the flow of money, collect taxes, distribute stimulus in a manner that will make the clunky, current Federal Reserve system obsolete. Robust alternative cryptocurrencies that fall outside of that sphere of control are inherently a threat. There's a non-zero risk that governments adopt the tech and choke off the currency.