There also the fact that China's Government would very much like to pretend nobody is opposing them.
Thus the Counsel being in the News is a No-No, since it gave the Democracy Advocates a greater platform and sympathy.
That's a given. With the possible exception of Bridge Man (the news of his action circulated internally
despite the usual heavy machine of censorship activating around all mention of the issue) there's probably a dearth of common knowledge within China about anything the top brass don't feel is germaine (or cannot spin to their cause).
I imagine in-country Democracy Advocates are whistling in the wind with what little internal publicity there is from this action. And out-of-country ones (like those who had the protests that led to this) can do pretty much as little about it, insofar as back-home is concerned, as ever.
Letting posters stand longer wouldn't be any more useful than (as hoped?) driving the protestors away. On balance, I don't see it having been better for the servants of the authoritative regime to have held back and risked an indeterminate escalation of protest
without any official reaction. Were all protestors going to even leave (and leave their material materially unguarded) at night? Doesn't sound like typical protestor behaviour, on balance, and doesn't sound like good anti-protestor taskforce behaviour to depend upon it.
Look (e.g.) at the wave of pro-Tibet protests in 2008, across Europe/the West in general. With the difference being that (in the UK, but similar to the French/etc situation with their own local services) the Met arrested individuals who were deemed to be ringleaders in a situation which was embarassing (politically) to the UK, in the year of the Beijing Olympics.
There's comparatively fewer political reasons to kowtow (fig. or lit.) to China, right now and several interesting new ones to let them eat a bit more of the general protesting. If the PM has any thoughts of having a say in the matter, they (he, she, and now whoever is next) have had other bigger concerns so there'll probably not be the same crackdown as then, especially after having had to respond (and positively so) to Hong Kong residents who have had their promised continuity of democracy dashed, and the de-facto alliance (or strict neutrality yet having a definite lean) with Russia. Amongst so many other things.
(I haven't heard much about
why Hu wandered off, 'escorted'. I suspect we're supposed not to know, at least until we're told (something, correct or not). I doubt he will be 'disappeared', but it does sound a bit like "gone to retire to my dacha (in Siberia)"/being put on the bus, rather than having to be put on trial for something to fully discredit (whichever nuancsd parts Xi wishes to discredit of) his legacy in order to reinforce his own. It could be full on Game Of Thrones stuff, or just "about time the old guy just retires". It could even have been Hu just asking not to be part of the new era, before it ever became necessary to be asked to do so. I don't think Hu has a comeback in him. But then I didn't think Boris did (one of those Comback Kids, I know, but I felt sure that this was it, this time) yet he's possibly going to surprise us. Definitely has the momentum to surprise us. Just needs to poke the right ultra-minority support-base at the right time.)