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 Human Resource Machine on Steam are 7 Billion Humans, SHENZHEN I/O, TIS-100, Turing Complete, while True: learn(). They rank highest because their Steam community tags overlap most with Human Resource Machine's — shared tags include Programming, Education, Puzzle.
How are games like Human Resource Machine chosen?
Every game is described by the tags Steam players vote on it. Rare, specific tags such as Programming, Education, Puzzle count far more than catch-all ones like "Indie" or "Singleplayer", and each game is scored on how closely its whole tag profile matches Human Resource Machine's. Popularity never affects the ranking.