More like a democracy with no term limits and a leader with 90+% popularity rate.

Sure, steam looks powerful, as if they can do whatever they want. But you have to look at why steam is so powerful, it's because people like steam. If steam uses that power for anticompetitive behavior, people will stop liking steam and it will lose a lot of power.

Just like if the leader does something that the people don't like, suddenly the approval rating is no longer at 90+% and he loses the next election.