User blog comment:Brandon Rhea/How we're testing the fandom.com domain migration/@comment-35268131-20181103163650/@comment-26269148-20181105031425

Mainly because the search engines might have internal links or caches that break due to the change, and/or might not put the wikis as high in the results list as they would've been before the change. So, it's mainly just that search engines needing a bit to catch up can influence incoming wicks from those search engines.