I think the theory is that without Musk, people might start valuing it as a car company, rather than a magic future company what was going to release self-driving farting flamethrower robots any day now. For all that it hasn't performed well this year, Tesla's valuation is still much higher than one would naively expect.

Amazon's a fairly different situation; no-one's really valuing Amazon on the basis that it might suddenly start doing something completely different and magical.