I remember how Bill Gates never thought that the Internet would ever take off. Also Edison thought we'd all live in pour-in-place concrete....
Yeah well, I don't think that Bill Gates is a genius. According to this interesting perspective,
What really made him rich was having been in the right place at the right time in 1981 when IBM needed an operating system for its new PC. Gates (with Allen) borrowed heavily, to put it gently, from an existing operating system, Digital Research’s CP/M. (For DR’s version of this history—“Microsoft paid Seattle Software Works for an unauthorized clone of CP/M, and Microsoft licensed this clone to IBM”—see here. A less biased, though still damning, look is here.) In other words, another instance of adopting someone else’s work and taking credit for it—this time with the innovation of litigating aggressively and manipulating markets to defend a monopoly position. Because once it secured that monopoly, Microsoft did everything it could to crush competition.
And Edison was rather similar. Edison used brute force discovery to solve the light-bulb filament problem, and used some, shall we say agressive business tactics to protect his business. In order to make people afraid of his competition (alternating current, Westinghouse), he used AC to electrocute animals such as elephants. He successfully campaigned to have AC used to execute death row prisoners (the electric chair). He was, IMHO not a genius.
Elon Musk is, in my opinion, a bona fide genius. With a bachelors degree in physics, he taught himself rocket science, and was the chief designer of an entire rocket, the Falcon I. This rocket managed to put two objects in orbit before being superceded by the Falcon 9. The amount of information he must have learned is astounding. Fluid dynamics, combustion, orbital dynamics and trajectory control, metallurgy, each in and of itself an entire field of study. He also has a solid background in computer science.
So, I will give what Musk says on the future of transport quite a bit of weight. He has earned it.