Using this statistics on the site, we can see the following history of the open, closed or deleted questions of the site, per month:
What we can see, is a slow, roughly linear expansion, which is the typical behavior of most smaller beta SE sites working actively on its graduation.
However, this tendency was broken, roughly in the second half of 2017. Then, the count of the new questions got a huge increase, but also the count of the closed/deleted questions with it. This is highly atypical. The result is that the count of the questions who survived the reviews, didn't grow significantly.
My impression is that from somewhere you got a gift, i.e. a large mass of content, questions, newcomers, and you rejected it. I am not sure if it was a wise decision, if your goal is to make your site successful.
What is happened?