Musk and Carmack are both rocket nuts. Carmack ran a rocket company: Armadillo Aerospace, mostly as a hobby. From engineer to engineer, Carmack has a lot of respect for Musk, and Musk tried to offer Carmack a job at SpaceX, as in "stop playing with your toys, we have serious rockets here".
But they are also pretty good at roleplaying engineers. I suggest watching the latest Tim Dodd videos when he tours Starbase with Elon Musk and you'll see Musk engineer character. No nonsense here, no Mars colonies or hyperloops, just the practical considerations of rocket building.
As for John Carmack, my preferred example is that short discussion with Elon Musk on Twitter. https://twitter.com/ID_AA_Carmack/status/536277962803650562
I still think the whole passenger part of spacex might be a pipe dream but who knows.
Elon Musk speaks quite aspirationally and optimistically from time to time, for both Tesla and SpaceX.
> SpaceX has delivered
They sure have! Tesla has also delivered over 1.7 million cars. They're on track to deliver about 750k cars in 2021 alone.