Matches come from the tags Steam players vote on each game, weighted so a rare tag counts for far more than one that sits on half the store. A game's popularity never moves it up this list.
The closest matches to App 1528120 on Steam are MOLEK-SYNTEZ, while True: learn(), App 1724140, Infinifactory, App 1289990. They rank highest because their Steam community tags overlap most with App 1528120's — shared tags include Programming, Automation, Science.
How are games like App 1528120 chosen?
Every game is described by the tags Steam players vote on it. Rare, specific tags such as Programming, Automation, Science count far more than catch-all ones like "Indie" or "Singleplayer", and each game is scored on how closely its whole tag profile matches App 1528120's. Popularity never affects the ranking.