I am guessing Musk was having a conversation in his mind, because as he's walking he makes certain movements, but as well nods his head to the left in a way that I have seen him do when he is speaking out loud. So as an Aspie, I am thinking that Musk is having a whole serious conversation in his mind and he's oblivious to everything else, and it is hilarious.
...
https://www.youtube.com/watch?v=xylS-tqiiyg