I think precisely because he is a critic of the AI development he is working on Neuralink. He thinks that, by having a direct connection between brain and computer, we thwart the AI doomsday predictions, because the AI will be an extension of us and we will be in a symbiotic state. This is Elon's way of insuring that AI won't destroy humanity.
Well, I am all for technological progress and applaud the many projects on AI development, but I still maintain that Musk statements were part of a FUD strategy. At the end of it, it's just a matter of making money.