They don't have to go after all of them, they just have to make an example of one. See: qwest's Joseph Nacchio: https://en.m.wikipedia.org/wiki/Joseph_Nacchio

If you get 75% coverage (or let's say the 5 biggest ISPs here, comcast and so on) you don't need to really chase the long tail of small providers that hard. It would effectively be unavailable to non technical people at that point.

six months ago I would have said the same thing about US universities.

> They could try, but not even China could build an impregnable firewall.

They can learn from Russia. Censorship in Russia now surpassed China. TSPU are now in every ISP facility. They pass all traffic through them and allow arbitrary bans of specific resources/protocols/etc in specific cities or whole regions.

I heard from a friend that went to China and the hotel staff right away asks if they want to VPN their room.

They don't need to. If only 1% of the people are able to access censored content and therefore hold censored ideas, the majority will treat them as crazy pariahs.

It's the same mechanism that makes us consider the 1% of flat earthers crazy. Sadly the mechanism works based on how many people believe a thing, not whether it's true, so it can also block true things if only 1% of people believe them.