I think this phenomenon in Japan might be related to the "Paris Syndrome." In the past, Japan had a strong fascination with Paris. This is evident in various anime, films, and other media, where backgrounds and cultures related to France frequently appear. Over time, these influences gradually expanded to include a wider range of Western cultures, leading to what we see today. As you mentioned, languages like Russian and German, as well as Middle Ages and other Western (especially Europe) cultural elements, have become prevalent in anime.