To answer this question, it is important to understand which keywords rank for which URLs of the domain and are thus responsible for the change in the overall SEO visibility.
Let's explain this with an example:
Our domain fruits.com shows a positive increase in visibility.
We find out in the winner keywords that the keyword "mango" has gained significantly in ranking positions and visibility. The keyword ranks with the URL "https://fruits.com/mangos".
However, we then see in the directories that the directory "https://fruits.com/mangos/" has a negative SEO visibility trend. How is this possible?
The explanation lies in the details. Directories are separated by "/" at the beginning and at the end. If the "/" is missing at the end of a URL, it does not count as a directory. In our example, the visibility of the keyword "mango" is counted under the directory "https://fruits.com/". For it to be included under the directory "https://fruits.com/mangos/", it would have to rank on this URL. So the "/" at the end is important.
This could also be interesting: Exploring the Declining SEO Traffic