Why don't I have a custom title by now?!
Nuxius has a lengthy explanation and a couple of solutions. Unfortunately, the first (and likely most urgent) of these two can only be done by the site owners:
The other problem is simpler to solve, we just need to redesign the front page (something long overdue anyway). The current front page is inherited from a wikia-mandated change (this was the previous layout). And yeah, we could tart up the Wikia front page to make it wikiaer. It'd help us and the wikia staff would like it instead of considering it as sabotage.
First, let's start with the easier to solve problem. This has to do with how Quasar has the various different domain names set up. Unfortunately, instead of just forwarding doomwiki.net and doomwiki.info to doomwiki.org (which is the proper way to handle multiple domains for one website) he mapped them all directly to the website. So you can use this website from any of those 3 domains, complete with 3 different logged in accounts if you wanted, because as far as anything outside of the server (ie your browser) is concerned, it is 3 different websites. And this includes Google. However, they're 3 "different" websites with the exact same content (obviously, since it's the same pages on the same server). In other words, duplicates, and of course as we have seen previously, Google has a method of removing duplicates from its results.
Another coincidence of this is that it temporarily spreads results across all three domains, so some will be from the .org one, while others will be from the .net or .info ones. It basically makes this wiki competition with itself.
And this leads us to another, in this case particularly damning, coincidence, in that having multiple domains mapped to one website is something unscrupulous websites used to do to grab more visitors (ie create one crappy scam website, then get a bunch of different domains with celebrities names in them and map them to that one website, that way you show up in numerous search results and get more visitors). I say "used to" because Google caught wind of this and now has it set up to actively punish websites that do this in their listings. So over time, more and more links to this wiki will disappear from the results as Google's automated processes weeds them out.