This is just a formality.
Obviously chans have been monitored since years.

Thing is, userbase is so random and posting style/interests that it's hard to actually spot "the threat one".

So they take the entire sites down to prevent the "threat one".

Leftwingers cheer for now, but if they ban everything on normal web, leftwingers are next, they are full of Leninists and Anti-Government Anarchists.