I think it's important to point out that the success of the company is largely built on the mythos of the man rather than the objective success of the cars. Tesla, earlier this week reached a market cap exceeding Toyota, and is larger than every other American auto manufacturer combined, despite having a fraction of the revenue. A lot of that is predicated on the "fibs" that
* All the "data" being collected by Tesla cars will be used to create full autonomous driving
* The battery technology will be so desirable that Tesla will sell batteries to everyone
* SpaceX will put a colony on mars, and they will only drive Teslas on mars
You remove Musk from the equation, and its doubtful that any other person could convince investors, fans, and potential customers that Tesla will ever accomplish of these things and tank the value of the company. If that happens it's clear that Musk will not only lose a ton of money, but ,depending on how profitable they are, they will lose their cash cow that allows Tesla to aggressively grow.