It's not really control
"We're not here to judge, we just want the money."
Any question as to whether or not the banking system is a huge scam, was irretrievably decided "yes" in the 2008 collapse. Trillions of $ "lost" only to be looted back from the $ via the magic of fiat currencies. No one went to jail. No one fined. Heck, it's not clear to me that there were even any serious criminal investigations. Meanwhile, people who had to slightest difficulty making their mortgage payments were foreclosed on. In the US, the foreclosers often did not even have valid paperwork to do so.
Cryptocurrencies threaten to put an end to that game. If you think that the US goes to war over oil, you've not seen anything yet compared to what will happen if the control of money by the central banks is seriously threatened.
Which is why I generally have stayed far away from crypto coins. Even if, history 100% to the contrary, a coin were set up that had all of the "right" features, was implemented by actual adults who have a clue about software & hardware engineering, and was somehow picked up by enough people that the problems of thin markets meant that daily, weekly, monthly, and annual fluctuations were no worse than fiat--that is exactly the point that the national governments move to destroy it.
How much of their "citizens'" money are they willing to spend to keep control? How much did they spend in 2008-2009? That's the floor. We know that they spent that much then. They will certainly do it again. They can buy enough compute power to become a majority of the miners. They can drive the compute cost to mine a coin up--and then turn off all of their miners. They can flood the system with so many transactions that recording takes days. They can custom design malware to attack miners and or the networks of the large mining groups.
Nevermind the things that nation states do when they get serious about having their way. Physical attacks, wetwork, passing laws....