It's not down at all, ChipMixer is still using .com domain but it is not being used for mixing but it is redirecting to .onion Tor domain.
I think several forum members was suggesting this solution even before it happened to reduce and avoid risks of clearnet domain getting hijacked again.
I have forgotten what happened but was sure that something happened lol and I thought they were down, haven't checked in a recent time. Did their clearnet domain get hijacked? I can't remember if I have heard about that.
I think that they primarily depend on geolocation. For example, as the first search result with DuckDuckGo I see a phishing site (cx), while with Google I also see a phishing site (xyz). It's the same with paid ads that you can see if you don't have adblock installed and turned on, because scammers target certain countries more than others.
Geolocation is a factor in search engine but most of the time they aren't and it depends on the optimization. Regarding what you said about Google and Duckduckgo, it's because of their robot/crawler. They rank websites based on their own criteria though most of them are similar. Besides, as a domain owner, you must also allow your site to be crawling in different search engines.