Google is likely their biggest inbound source of traffic, so they're probably experiencing a marked revenue drop as well.

It's unfortunate that so many livelihoods are subject to the capricious whims of a single company. A company that is increasingly seeking to keep users on their engine without sending eyeballs or revenue to any third parties at all.

We're watching Google's "embrace-extend-extinguish" arc for the web. It's not over by a long shot, but they absolutely intend to finish the job.

Source: a small wiki I help manage, for an obscure game with <10k players, recently had to disable new signups, because the spam was so bad (and it was stuck on an old version of MediaWiki, which didn't have CAPTCHA-support).

On a popular wiki, and it sounds like this one was fairly popular, I imagine even CAPTCHA's won't be enough to stop wiki spammers. If those spammers were posting more than just "buy my penis pill" garbage (e.g. they were putting links to malware sites), Google probably, and somewhat legitimately, saw them as a source of such malware.

I imagine the fix for the OP is a thorough audit/cleansing of all malicious content on the wiki, followed by some sort of appeal to Google (which will no doubt take months, if they even respond at all, because ... Google).

Really OP's only hope is that the Google team responsible for this has an Italian Pokemon fan; otherwise they are probably screwed.

There's a lot of delayed cause and effect in search, and it's much easier to make a minor mistake that excludes 0.1% of websites from crawling or indexing than it is to detect that it's happened except from affected websites telling you about it.