he’s not trying to leave his mark on history

He kind of is, but in the way old-school millionaires did - he has purchased a MASSIVE yacht and turned it into an ocean-floor research laboratory, either donated it to a university, or just allows researchers to use it.

Gabe was already wealthy with Microsoft money when he founded Valve, so when his new private startup found success he didn't feel the pressure to go public, expand, dilute, and cash out. He made the judgement call that they already had enough talent internally to keep playing the hits while keeping all the profit for themselves, and he was right. I'm sure a little bit a business ideology reinforces Gabe's long-term outlook for Valve, but he's ultimately enabled by a happy intersection of pre-existing wealth, great timing, and careful hiring choices.

I mean, he is developing the brain chip with his Starfish Neuroscience company but its supposed to be minimally invasive and let's be real if its between his and Elon Musks (which is NOT minimally invasive and requires surgical implantation) I'm definitely going with his.

I wouldn't say at this point its all about gaming though. Valve is, but not necessarily Gabe. Which I don't mind but I could understand how some people wouldn't like it.