Carmack made multiple fundamental breakthroughs in 3D graphics. Not only that, but he consistently positioned himself to commercialize those, which is not easy. His Quake 3 engine was the bread and butter of Id Software, generating billions in revenue.

In recent times, he's done coronavirus simulations (I don't know anything else about that), and is doing AGI research.

He's also a true hacker through and through. Simply having an example like his, as a model to follow, is helping humanity. I happen to be human, and I distinctly remember his .plan files influencing my decisions in a positive way since I was 13 or so.

(The line about getting a hotel and accomplishing as much as possible in 2 days of focused effort was particularly impactful.)