Full moon "articles" are basically the lowest of low effort content. Full moons happen on a schedule (a schedule that other people have already worked out for the news sites so they don't have to do any original work), there's basically nothing new to say about them, but you can still run advertisements against those articles. The moon also conveniently dovetails with the reader demographics who think astrology and horoscopes have real power. It's basically free money, and I think that's the causal driver because we know that news rooms have been in decline for a while. Real journalism is hard work and costs time + money, clickbait is effortless and cheap to churn out.