How do you know this? I am genuinely curious. Maybe I am quite mistaken here.
My guess in magnitude is traffic by accident < passive traffic by being indexed < promotion. And I further guess that most games that do promotion will be higher than games with only passive traffic in the popular ranking. In a genre like horror, there are just so many games. Your main source of early traffic has to be promotion, else there will be no real difference between being indexed or not. Not in horror where there are so many new games each day.
You could at least talk about your game at the places where this is allowed. Like the release announcements.