How do you plan to enforce the ban? Fine any Chinese companies that buy ads on Google? How do you identify the Chinese companies? How do you identify their business registrations so you can send them the ticket?There are plenty of other avenues to sell ads - TikTok (topped Google for being the most visited resource btw), Twitter, buying directly from influencers bypassing Google Ads, etc. Either way, Google should be forced to fell the pain.
Government can't just issue a diktat, it has to think of the logistics of enforcing the diktat as well.