Prior work helps, but its not needed. Obviously if you make a game good enough, you can make it successful even if it’s the only project in your profile.
But especially in the beginning, if you have a profile with 10 (let’s say) mediocre games, and suddenly you upload a big hit, there are people who will be more likely to try your game, as they see the progress. Not to mention that you would already have some followers, or people finding your other games and seeing “more from this developer” and will end up in your new game.
It’s just an early boost, it is definitely not required.