Indeed, the main difference between Mr. Musk and Silicon Valley’s fallen heroes is that he has been able to deliver on some promises: Tesla does make cars, and SpaceX does land rockets. But as a number of old promises like fully self-driving cars appear to be more aspirational and less plausible, the distinction between him and those fallen heroes is starting to lose its meaning. His long list of unfulfilled commitments — a fully solar-powered electric vehicle charging network, a fully automated manufacturing system, an autonomous minibus and even a rocket-powered flying car — wildly exceed his achievements.

By moving to buy Twitter, Mr. Musk has not only added another distraction to his long list but has also already shown the same drive to announce sweeping decisions in public. While he had some success in realizing user features at Tesla, his contradictory goals of increasing algorithmic transparency and eliminating spam bots on Twitter are the most obvious sign that he intends to impose his will on the service without drawing on the expertise of workers who have been wrestling with Twitter’s thorniest challenges.

Ultimately Mr. Musk’s goals for Twitter, as they are for Tesla, are not about making the right decisions for his companies or the people who make them possible. They are about playing to the crowd and burnishing the legend that keeps fresh bodies and minds moving through the businesses that chew them up and spit them out. Now if Twitter falls into his control, Mr. Musk will have seized the means of making the product he has always cared about most: his own myth making.