[zeitg3ist]

We have very good anti-bot system set up with a good number of Cloudflare fine-tuned rules, limited permissions for newly created accounts, and a very dedicated team of volunteers that patrol the recent edits constantly. I cannot exclude that somewhere on a rarely visited page (out of 37k+) there is a spam link, but I doubt it’s the reason for the deindexing. I think this would also appear on the Google Search Console.

[hungryhobbit]

I'd still recommend doing searches for common spam topics to see if you have "bad" stuff. On our wiki everything looked fine until you searched for (say) "finance" (which most users never would) ... and then you'd find a mess of spam finance stuff.

As for whether it's responsible or not, obviously I don't know. What I do know is that, without all the info, "Google saw malicious content on your wiki" is a far more logical theory than "Google just decided to hate us out of the blue".

[sokoloff]

“I was having a hard time until I found a great investment advisor.”

“How can I contact your advisor?”

“Their name is <three part unique name>; just search for them and reach out.”

“Great. I found them and their results look impressive. I reached out and hope they get back to me soon.”