Nearly 100% π
For one thing, China may have a significant foothold in the bitcoin world (not nearly 100%), but even with a coordinated effort of all private miners, the amount of energy and cost they would have to expend to crash bitcoin would be enormous.
And why? The Chinese are not financially ignorant like most westerners, they benefit far more from utilizing bitcoin than attacking it.
These kind of paranoid conspiracies always come from a place of fear, and it's inevitably either someone who doesn't use bitcoin because of security concerns while they trust their bank with USD, or it's some shitcoiner shilling their scam.