> ironically, most of these companies are out of China

Of the three companies named:

- Google's user-facing services (search, email, app store, docs, ...) are blocked, but Google Ads (which are censored) and Android (which comes without any content that would require censorship) are still sold.

- Microsoft: I'm not aware of any of their products being unavailable. Windows is the dominant desktop operating system in China, and I'd be surprised if the app store wasn't censored. Bing search results are definitely censored (they tell you so at the bottom of the page).

- Amazon isn't selling much that could run afoul of censorship, except possibly books (remember when Amazon used to be an online bookstore?) but in China their market is mostly targeted at the niche of high-end imported goods. (Note the country-of-origin indicators on https://www.amazon.cn/ )