Games often link to the "official" reddit community from inside the game, so no surprise that traffic will be driven there
But even besides that, if you look at any time this situation happened in the last ~3 years, you'll always see more users being vocal about the preferring the official sub than the community one in comparison.
Reddit's demographics changed, and it just exploded over the last couple of years with "casual users", "went mainstream" or what ever one wants to call it.
Most users these days don't even know that "official subreddits" were something that was super unpopular and uncommon on Reddit.