Actually, you can trust neither Guo nor the PRC regime. Both are known liars. (Guo is, btw, also the guy who announced that declaration of martial war in Hong Kong would come around 4 August.)
It's almost impossible to become a billionaire in China without corruption & connections to the CCP. & it would be naive to think he "defected" because of moral considerations. He probably supported a CCP faction which lost an internal power struggle & had to flee because else he would have lost everything, foremost his freedom.

You don't need confidential information to see that the CCP wants to become a hegemonic power, but that's a long term goal. The PLA is still much too weak to win a war with the USA. The best they could hope for is to keep US forces away from the Chinese Pacific coast. At the moment even the probability of a successful Chinese invasion in Taiwan is pretty low.

Bitcoin miners may be located to 60% in China, but that doesn't mean the (central) government controls them. Some operations are completely illegal, others are by private companies, others by companies under control of regional governments. Organizing a 51%-attack would be much harder than you seem to think.

& even if they could: So what?
BTC is not that important to the world economy. Many people would suffer losses, but else not much would happen.