Many problems, first of all, technical problems. At present, the best technology in China is 28 nm, but intel and others are very mature mass production 14 nm technologies. As for the second market problem, even though the CPU produced in China is facing an embarrassing situation that there is no market, and the third one is limited by the patent pool, foreign manufacturers have applied for many patents to restrict others from entering this field, just like a pool, so it is difficult for people to bypass this patent.
Of course, China is not without its own CPU. There used to be Godson, but now Huawei's Kirin mobile phone CPU is also booming in the mobile phone field.