I don't think that governments will ever prohibit new cryptocurrencies from being developed. I don't see cryptocurrencies as a threat for fiat currencies. They have completely different systems and their goals are also different for people. Rather than these cryptocurrencies, the biggest threat for fiat currencies will be the digital currencies which are developed by governments. Because in the future, they will start replacing fiat currencies one by one.
You may say that it was not the threat for fiat but unfortunately, and from the government's insights this is a big threat for them. The biggest concern is to have control over crypto which was impossible and creating their own digital currency is their way to combat the spread of crypto.
The government couldn't prohibit the creation of crypto but it was the SEC to find a way on how to stop their project. Many issues had rise concerning these and many crypto projects have been also dissolved with their actions.