Watching what’s going on at Twitter is like watching a guy losing his mind in slow motion. The guy in question is Elon Musk, who once upon a time was the world’s richest man and now isn’t. (That slot is apparently occupied by Bernard Arnault, the luxury goods mogul.) Musk is in a hole but apparently doesn’t know Denis Healey’s First Law of Holes: when you’re in one, stop digging. The funny thing is that he dug the hole himself. First, he paid way over the odds for Twitter. Then, when Tesla shares (the main source of his wealth) tanked,...