I don't know the specifics behind why the communities were (re-)removed but the reasons given in the modlog seem vague enough to apply to anyone linking to Google or YouTube as they reference or indirectly link to piracy:
Removed Community CrackWatch@lemmy.dbzer0.com
reason: facilitating piracy, referencing websites used for the distribution of copyright infringing material in images
Removed Community Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ@lemmy.dbzer0.com
reason: facilitating piracy, indirectly linking to websites used for the distribution of copyright infringing material
From the initial removal announcement post:
The discussions that have happened in various threads on Lemmy make it very clear that removing the communites before we announced our intent to remove them is not the level of transparency the community expects, and that as stewards of this community we need to be extremely transparent before we do this again in the future as well as make sure that we get feedback around what the planned changes are, because lemmy.world is yours as much as it is ours.
EDITED multiple times due to confusion over origins of the ban.
Shit, sorry for all the drama if this is just me misunderstanding the federation system. I wish there was more information provided in the modlog than just "admin", like at least stating the origin server that took action. I just assumed since those communities had been "supported" (or at least tolerated) by db0 for so long they were on good terms and in communication with each other - didn't even cross my mind.
EDIT: db0/dbzer0 had nothing to do with this ban, it was performed by a LW admin.
No, you're not misunderstanding anything. The communities were banned by lemmy.world, specifically @MrKaplan@lemmy.world, one of the new admins. At a guess he probably took action on his own without realising the consequences.