If they executed a 51% attack, it will most likely result in a hard fork. Every full node would be able to tell where China branched off. We'll have BTC and BTC-China, with their individual markets. Keep in mind that while China has the bulk of miners, the majority of reachable full nodes are in North America.

Why haven’t they destroyed it then?

Frankly, because it’s not as much of a threat as the popular narrative suggests. They may actually benefit from being able to use cryptocurrency for their own ends, either by using it directly or using the public ledger nature combined with their surveillance powers to get insight into transactions.

Regardless, the attacks described here require large concentrations of mining power. In theory, the best way to attack it would be to wait for (or even encourage/subsidize) your country to become the geographical leader in mining operations.

Or even better: Wait for companies in competing countries to start holding BTC on their balance sheets and consumers to put their investments in BTC. Now you have a kill switch for part of the balance sheets of competing countries.

I personally doubt this is happening, but I’m sure it’s being considered as an attack scenario.

If anything, a government might even like a public ledger of all transactions. Sure, you can sell in person, and then it's about as secretive as cash.

I think at least part of the reason is because they own it. Per https://www.statista.com/statistics/1200477/bitcoin-mining-b... 65% of all bitcoin mining is in China, this means majority of newly minted coins are in China, but also they can launch 51% attack at any time.

It's not inconceivable (to me at least) that at some point in the future it would be politically or personally beneficial for the leadership of a totalitarian government to do something that is economically costly to it's citizens (in this case we're talking about damaging bitcoin, but it could be anything).

1. If you watch the market - it dumps each time when it's 9AM in China. The moment the miners wake up, they sell the BTC. It creates an inflow of foreign currency into China.

2. Traceable currency.

3. Soft power / control of narrative? Bitcoin seems to symbolize people's loss of faith in fiat system, and their governments.

They may be using it to track people attempting to move money out of the country.

Cryptocurrencies aren't very anonymous.

In an elegant tautological argument: because at the moment it does not advance their causes to do so (yet).

Better stuff to do ?

This is the Turkey Fallacy.

No, I'm actually asking for ideas for why they haven't destroyed it yet.