The accusation was that Jimmy Wales favoured the deletionist faction on Wikipedia in order to push as much content as he could get away with over to Wikia, where he could monetize it. Once a wiki had been created there, it would be very hard for a different wiki to compete, since Wikipedia lent a huge part of its SEO juice to them.

Wikia/Fandom regularly takes over wikis that try to migrate off the site and scrub the attempt. The biggest recently was the Terraria wiki. The fandom wiki still outranks the official in Google.