RISC-V is free and open as in libre, by contrast to x86 and ARM which must be licensed from Intel/AMD and ARM and are thus subject to potential western economic sanctions.
Now, yes, China will just espionage and kangaroo court their way through and around such legalities anyway, but nonetheless RISC-V is less effort for more reward for China if it becomes at least on par with x86 and ARM.
Put more basically, it's a matter of national security. China can have an entire RISC-V ecosystem indigenously, unlike x86 and ARM.
If the US and/or UK place sanctions on exporting microprocessor technologies to China then that's that. Intel/AMD and ARM are subject to US and UK laws and regulations respectively.
RISC-V by contrast is much, much harder for any given country to regulate because of its free and open nature. At most the US and UK can embargo individual developments made within their jurisdictions, but they can't regulate the entire architecture. RISC-V doesn't have a kill switch named Intel/AMD or ARM.
ARM China is a wildly different animal than ARM. They went rogue a few years back and though SoftBank/ARM did a lot to get things back in line, it still shows up like this:
Now, yes, China will just espionage and kangaroo court their way through and around such legalities anyway, but nonetheless RISC-V is less effort for more reward for China if it becomes at least on par with x86 and ARM.
Put more basically, it's a matter of national security. China can have an entire RISC-V ecosystem indigenously, unlike x86 and ARM.