With a computer of such power, you could crack bank accounts, any online account. Pretty much anything so why would you waste it hacking bitcoin wallets when there are banks full of suckers' money?
The government (Chinese or any) can already crack any bank accounts and online accounts. It's the bitcoin that's giving them a headache. China (as well every other country) are moving to a complete facial surveillance and they want every of the transaction to occur online on the governments term. Bitcoin is a way of evading the surveillance. Bitcoin is also associated as a tool to hide the wealth form CCP in China. China have reasons to allocate resources to stop bitcoin. They don't need to steal it.