Tell HN: A case of negative SEO I caught on my service and how I dealt with it

Recently, my service https://next-episode.net experienced a huge drop in Google rankings. As I've been running it for more than 15 years, this is far from the first time this has happened. Usually I've been able to attribute big fluctuations (positive or negative) either to something I did, a Google algo change, or some external factor. For example, about 2 years ago, something similar happened. While digging through my Search Console I discovered that Russian websites generated thousands of links pointing to a page on Next Episode with pornographic keywords used as link anchors. This was so effective that they managed to get those keywords to the top of the "Top linking text" in Google Search Console - naturally (most likely) resulting in drop in rankings for the regular keywords and the domain in general. About a week ago, while trying to investigate the current drop in rankings and browsing through my "Latest links" external links export from