I tend to think Musk earnestly believes he can jump into any field and (with his team) revolutionize it over night, rather than this being a PR stunt per se.
When your big idea is a square peg for a round hole and you publicize it before you've checked that, the difference is indistinguishable.
“It wouldn’t have made the first 50 metres into the cave from the dive start point. Just a PR stunt.”