Steam mostly uses the Snowball effect. If your game sells well, it gets listed and suggested more, if it keeps selling well, that will happen more and more until it snowballs.
It’s hard to find any solid numbers on how it exactly works, we all know Valve likes to keep things behind closed doors, but from what I’ve heard, if you your game has a higher than average consumer view:purchase ration, that’s when it’ll start getting listed more. But there may be more variables that help the snowball.