it's less risky for an individual in the leftist hivemind to smear a target that has already been "approved" for unpersoning. especially for the more opportunistic of the lot.
they want to instill fear in bystanders. while an official witch hunt is ongoing against a target, anyone who takes the side of the target would also get destroyed. it's harder to enforce this when they attack too many targets at once.
Also:
Agreed on both points.