This is really a bizarre situation that is being currently discussed in a Turkish online forum. The reason becomes quite obvious when links to these pages are checked: They are all AMP pages. Yandex is associating these highly visited or searched pages with Google since they all seem to be hosted by Google.

The search in question is here: https://yandex.com.tr/search/?lr=11504&text=google

You don't have to have a perfect Turkish to understand the word "porn" under Google affiliated sites.