Because he has a rare combination of traits which allow him to operate effectively under extreme stress. You will begin to understand this after you've experienced moments of high personal stress where you were also asked to perform (or wanted in retrospect to perform).
Here is an example from a friend of mine who went to USC with me, you're in a store and someone comes to rob it with a gun, the police arrive before they finish, and they line you up with the other customers against a wall, wave a gun at you and threaten to kill one of you if the cops don't let them go. The police storm the store and shoot the perpetrator dead right in front of you. Outside, sitting in the back of an ambulance being checked out, the detective comes over and asks you "What were the other customers wearing?"
Now in this case the police thought the guy had an accomplice who was pretending to be a customer when it went wrong. My friend realized he could remember nothing of the event other than the end of the gun barrel, and that the noise of the gun shots when the police stormed the store made the take down some sort of sad silent movie. Under that level of stress he just stopped thinking. And the police assured him that was absolutely the normal way of things for people who had not be trained to deal with these situations.
The CEO of a company finds out that there biggest customer has just cancelled its "non cancellable" POs and the company is not going to make payroll if they don't do something in the next three weeks.
Being able to operate under stress, being able to make good decisions under stress, things that Elon has demonstrated a number of times (and yes sometimes the stressful event was his own fault but it didn't take him out of the game)
And getting people to do something well. Easy to say hard to do, they have to want to do it. As you manage more and more people, you will get to experience a diverse set of personalities and traits, the larger the group the more diverse and the harder it is to get all aligned. To be a successful leader in a large enterprise you have be able to get the best out of people, even when they may not like working with each other, to achieve a larger goal. Bigger the group, the harder that is to do effectively.
So you take him out of the equation, and the reset falters. Take Steve Jobs out of Apple and Apple headed for the toilet. Put him back, and it comes back from the dead to the largest company in the world. Sure that is the work of thousands, but the guy inspiring those thousands has a disproportionate effect.
Over your career you should evaluate your CEOs. Some will be great, and some will be horrible. Look at what the company accomplishes under great CEOs and what it accomplishes under horrible CEOs. Do that enough and you'll develop a healthy regard for Elon has pulled off in both Tesla and SpaceX.