I'm sure Karpathy did a good job at Tesla to make self-driving cars - as good as anyone could have, anyway. But it's better for the world to have him back as a teacher/blogger/YouTuber/popularizer.
I can't recommend enough this "backpropagation from scratch" from heremy howard (fastai) where he implementes backpropagation from scratch using python.
Can’t imagine the stress levels he had to endure at Tesla. Looking from the outside it seems totally worth it - he solved “the money problem” very young. Now he can do whatever the hell he wants and he keeps building because that’s what builders do. He’s such an inspiration.
Karpathy is awesome and I love that he's doing this and going down this route. (Hope he doesn't get that "offer he can't refuse" like carmack predicted and keeps doing educational stuff for us all :).)