if the government wants to control bitcoin by controlling 51% of bitcoin circulation then how much money they have to spend while, they will print as much money and make fiat into goods that will no longer be worth it. and if the government manages to control 51% of bitcoin circulation then i will sell my bitcoin and buy another altcoin then wait to buy the bitcoin price drops..
Regulators will do their best to control cryptocurrency in the same way they control fiat money. I will even say that with the help of a regulated cryptocurrency, governments will get full control over the movement of people funds. And without regulation, they will not allow cryptocurrencies and bitcoin in particular as a means of payment in the state.