Google prioritizes results that they consider more valuable.
Imagine someone looking for a private equity firm database, they WON'T type private equity firms, as those who enter that are either looking for the meaning of "private equity firms" or news about "private equity firms".
Google might have ranked you on top for some time, but after the release of hummingbird, everything changed, now Google tries to "understand" what you are thinking, what you are looking for and present the best possible results, not only based on the query itself, but also taking into account search history, habits, etc.
You should also consider that your Website, compared to the others shown for that specific query, has a very low domain and page authority. Plus it lacks of any kind of social signals.