9/11 was a gamechanger in so many terrible ways, not just for the United States and for our own national security apparatus but for the whole world. And those attacks blew apart any notion of separation between foreign and domestic threats, any notion that such attacks only happen to other people in other countries.
China has national security laws that compel Chinese companies to provide the government with information and access at their government's request. And virtually all Chinese companies of any size are required to have Communist Party 'cells' inside them, to make sure the companies stay in line with the party's principles and policies.