I made my living from being #1 in the world for the term "Koh Samui" in Google for more than ten years. Then, I got penalized for my SEO and dropped +50 positions. My income was instantly reduced by 60%.
I have no idea if this is the case here, but this is how Google works. There are hundreds of factors to get a good ranking in Google's SERP. Exact matched keywords don't have same relevance as they used to have.