Good wholesome Country A wants to spy on evil unknowable Country B. A forces A's companies to build in backdoors for A's spies to use. B buys A's products. A spies on B. B knows they're being spied on, figures out how, and starts spying on A because A also uses A's products. A knows this, but accepts it as the cost of doing business and keeps telling companies to include backdoors.

US and China: How Chinese Spies Got the N.S.A.’s Hacking Tools, and Used Them for Attacks

Chinese cyber association calls for review of Intel products sold in China

China and US: US finds Huawei has backdoor access to mobile networks globally, report says

But this applies to any combination of countries. It's just the way things are done! No country needs someone to have their fun video app installed to get at that person's data. Why can't they all just admit that it's a propaganda war publicly? No one will give a shit.