Speaking honestly as a foot soldier employee, I look around myself and I think you could swap out most of the people around me, including me, for most other people in our industry and the company would continue just fine. In fact that happens naturally over time anyway. The work we do is essential, but as individuals we are not essential. If I quit and move on, how many investors will reconsider their position in my company? Give me a break, and they would be right to not care.
It's about leverage. It's all about where you stand and how long your lever is. Musk stands at the top and he has a very long set of levers. He's also much more closely personally involved in engineering aspects of a company that most CEOs know little to nothing about. Sometimes that's good, sometimes it's bad, because his decisions have massively outsized effects because of this. Leverage.
If Musk makes good or bad decisions over the next few years, that matters much, much more than the decisions of anyone else at Tesla, especially because he hires and fires everyone else at Tesla. They're all only there, as individuals in particular, because of him anyway.
As it happens I think his decision making has deteriorated significantly recently, in some respects but not all. Also Tesla just doesn't have the magic special sauce SpaceX has had since they developed reusability. There's no special engineering insight in the Tesla architecture. Other vehicle manufacturers already caught up. That catch up is happening in space tech as well with BO's recent booster recovery, but SpaceX still has a very significant lead there, based on a truly revolutionary concept (which Musk championed personally) that they had exclusively for 10 years. Starship still doesn't work though, so we'll see.