Elon Musk wants to save humanity. That's his stated mission. He doesn’t want to get rich for its own sake, he wants to get rich so that he can devote his wealth to the colonization of Mars, which in Musk's mind is not only an enticing place to live but also an effective backup location for our species should something terrible happen on Earth. He believes we need to develop a self-sustaining, independent Martian civilization, because otherwise we are limited as a species to a single planet, and subject to a single-point failure known generically as Doomsday.