Not to mention all the fees they earn as an intermediary to buying ~every modern PC game.

Obviously. The point was that earnings from half-life were effectively the stand-in for investor capital. And I'd wager that even with all that money, or ten times as much, Steam would not have been able to establish itself without hl2 as a tool/vector. It's been almost two decades that we haven't seen a single steam copycat that did not try to ride a flagship game release in exactly the same way (unless you consider GoG or humble as steam copycats, or Playstore and whatever itms is called these days)

Yes, and now we are living in a reality where Steam has taken over ~all meaningful, non-niche digital PC games distribution. They got into a monopolistic position during a small time window of inflection where the market was transitioning from physical to digital distribution. It's meaningless to talk about the past in these circumstances, unless something truly drastic happens to open another such window to let someone displace Steam.

Heck, Microsoft followed exactly the same trajectory some years earlier, to the extent that their operating system is still synonymous with the idea of a desktop PC outside of the US (which I understand leans heavily towards the Mac, somehow). Their position is showing signs of crumbling only after multiple years of neglect and outright self-damage to their OS. The stability of a monopolist position locked in early is sometimes greatly understated.