The Mate 30 got hit with the US ban hammer. So Huawei never manufactured all that many of them.5G has been available since Mate 30. No surge like this during Mengwanzhou arrest era. And even then, Xiaomi dont use huawei 5G?
They couldn't order the manufacture of more SoCs at TSMC. Google services were disabled on it which meant a lot of people outside China would balk at buying such a phone. Some imported chips like the RF chips were made in the US and no longer available. Etc.