With Google’s Countless updates every day, the recent short-lived update is test dropping the Featured Snippet from the main core Web Results if yours is a featured Snippet on Google Search results.
If a site is selected as a Feature Snippet, then it will be displayed at the top of all the results within a box. Also as one of the search results within 10 core results of the same page. Now this will change as Google will drop that if the site is already featured. Google stated that this was set up for the best possible user experience.
Google has reportedly declared to Search Engine Land that this as an attempt and not as a permanent act but expected to be permanent in forthcoming days.