The concept of crypto itself isn't a ponzi scheme - it's decentralized money. You are saying they would never allow it to be mainstream. In theory that may be correct, but they would have a hard time enforcing it in a true crisis.
Turkey will provide us with some real world experience - because they officially banned Crypto for goods and services in March, and are eyeing further regulations. Yet bitcoin is trading at an all time high in Turkish Lira. Why?
To protect yourself from a hyperinflation like what is happening in Turkey, with a leader that has no clue about the currency market - the only safe place for the masses will be gold or crypto. You have cities in US with professional shoplifters that don't get arrested and walk in and take up to $950 without anyone doing anything. When a panic eventually happens in a more developed economy, you think people will listen to central bank rules?
Much of the worlds inequality are tied to central bank policies...so I don't think many people on both sides will really be defending them when the next financial crisis hits.