Based on your comments, I don't think you understand what a 51% attack is.
51% Attacks have to do with controlling >50% of the mining network hashrate, not >50% of the circulating supply.
*Also you don't even have to have >50%, you can perform a 51% attack with only say 10% of network power, you just need >50% to pull it off more often than not
If China has >50% of the mining power (a much more realistic claim than owning >50% of bitcoin) then it's surely just because a large mining pool is based in China, not because CPC actually has that much processing power on the network. Miners from all around the world would be connected to that pool and if they tried to mutate the blockchain those miners would simply switch to a different pool that isn't messing with their potential mining rewards for nefarious purposes).
As for a large amount of mining going offline, the bitcoin network is dynamic, it automatically adjusts the complexity based on the network hashrate, so if half of all miners got taken out all at once nothing would happen, the same amount of bitcoin would be minted, blocktime would be the same, network speed the same
Based on your comments, I don't think you understand what a 51% attack is.
51% Attacks have to do with controlling >50% of the mining network hashrate, not >50% of the circulating supply. *Also you don't even have to have >50%, you can perform a 51% attack with only say 10% of network power, you just need >50% to pull it off more often than not
If China has >50% of the mining power (a much more realistic claim than owning >50% of bitcoin) then it's surely just because a large mining pool is based in China, not because CPC actually has that much processing power on the network. Miners from all around the world would be connected to that pool and if they tried to mutate the blockchain those miners would simply switch to a different pool that isn't messing with their potential mining rewards for nefarious purposes).
Not according to any data I can find
https://www.statista.com/statistics/1195753/bitcoin-trading-selected-countries/
As for a large amount of mining going offline, the bitcoin network is dynamic, it automatically adjusts the complexity based on the network hashrate, so if half of all miners got taken out all at once nothing would happen, the same amount of bitcoin would be minted, blocktime would be the same, network speed the same