seo – Google Mobile not displaying thumbnail

Why Google Mobile Search does not display thumbnail for websites even if schema.org, meta tags and OpenGraph tags are all correct and follows SEO best-practice? As you can see from the following example (Official Website result) https://www.google.it/search?q=brand+new+heroes. The page is filled with opengraph tags, json+ld schema, main image is placed above the fold and wrapped inside h1 tag with alt proprety correctly set.