It's pretty obvious that Google et al. do a lot of "custom" filtering like prioritising Wikipedia, removing porn from "obviously non-porn" searches etc. (That "Berlin" search gives porn as the 8th result.)

I doubt that Google prioritizes Wikipedia deliberately. Wikipedia has tons of backlinks, authority, trust, typically a high text to html ratio, probably a low bounce rate. Moreover, it is fast, works well on mobile and on and on. It's is just a very well done and useful site for users and search engines.

My thoughts as well. They don't need special treatment to be in the top 3.

Wikipedia being ranked high is even an indicator for SEOs that an affiliate niche is not very competitive.