> I couldn't find the "tank man" censorship problem, and I looked.

You can just search for tank man to get a picture of it: https://sm.pcmag.com/t/pcmag_au/news/b/bing-image/bing-image...

> I'd never heard of "tank man" as a meme; I'd have looked that up under Tienanmen Square.

It may not be the ideal search, but look at how there are no results. Clearly some kind of censorship mechanism triggered.