Earlier quoted context omitted.
Karpathy in particular has built an excellent personal brand, lots of which is through his blog. It seems that technically backgrounded "explainers", á la Neil deGrasse Tyson or Richard Feynman, Elon Musk or even Bill Nye, can credibly straddle both expert and layperson worlds. People like to feel like they know what's going on.
Part of me dies inside every time I read the phrase "personal brand". I think it's sad that it is no longer enough to be good at what you do--you need to self-promote, blog, and talk talk talk in order to make it these days. What happened to also recognizing the quiet but competent craftsmen?
There area millions of quiet, confident, competent people across industries. People who reliably turn out high-quality products and are well-paid for their work. They get on well with their colleagues and progress with their career at a decent pace. You just don't hear about this much. Doesn't this count as making it?
I'd say that the reason you hear more about people who are well-known is essentially just because they are well-known :)