The government can actually control bitcoin but that requires quite a lot of money because so far it requires a lot of money to control bitcoin. Apart from that, the government also doesn't want its citizens to suffer losses because of the very unstable and very dangerous movement of bitcoin prices.
How government control Bitcoin?
Although the government has huge money, it doesn't mean that the government can control Bitcoin. Why do you think having a lot money enables the government to control Bitcoin? Bitcoin system is decentralized, there is no way to control Bitcoin. The price of Bitcoin is depending on the demand, the government also can't determine the price. If the government wants to secure the citizens, the government can give education about Bitcoin to them.
The government will never be able to control bitcoin. as you said bitcoin is decentralized, so no one can control bitcoin. Even though whales can manipulate it, it won't last long. because demand determines the rise and fall of the price of bitcoin.
If you look at the current conditions then I believe the government can control bitcoin, we know that whales have an important role in bitcoin price movements, imagine that the whale is the government, then it's the same, only the government doesn't dare to do that because they think to always building the country's infrastructure without disrupting the country's finances.