There’s simple and there’s oversimplified. The element your missing is “trust”. The reason gamers go to Steam is because we trust their reviews and return policies.

The other storefronts haven’t built that trust. Most gamers have the experience of trying other storefronts, hating them, and going back to Steam.

People don’t trust Gabe because he’s a billionaire, they trust him because he consistently makes decisions that gamers benefit from. No other game store CEO can claim that with a straight face.