I stumbled on this example of how a user with apparent issues went on a brief spree: https://www.wikidata.org/w/index.php?title=Special:Contributions/Piely01pi&offset=&limit=500&target=Piely01pi Commons:Administrators' noticeboard/User problems#Piely01pi
I can’t see how we (Wikimedia communities collectively) could have responded differently, and hope the person is getting whatever help they need in real life. Unfortunately a tool that allows users to make numerous, small, rapid, beneficial changes also allows numerous, small, rapid, detrimental changes.
Are you monitoring reversion rates, and who is watching the Wikidata Recent Changes feed for Suggested Edits tag?