They aren’t just beating the competition by being better.
They’re beating the competition because they don’t allow developers to sell games cheaper than on Steam if they want to sell on Steam. And they have the market share to be able to make it financial suicide for a developer/publisher to not put their game on Steam.
“You can sell your game anywhere as long as it’s cheapest here” smells a lot like a monopoly.
Makes sense to you. To me, it seems like they want a monopoly.