

Huh? Steam is absolutely a monopoly in PC game sales.
Monopoly doesn’t mean there are no alternatives. It means controlling an overwhelming share of the market.
Even Google has a monopoly w.r.t. search engines despite controlling less of its market than Steam does. If your site is deindexed by Google alone you might as well not exist for most of the population.
Am I missing something here? Just because Steam doesn’t violate the (comparatively weak) US antitrust law does not make it not a monopoly. Especially when there are clearly legal ways to have a monopoly according to point 2 and point 3.