It's easy to say that it's probably possible to land a orbital rocket first stage. But who would bet a multi-billion dollar business on being able to not only do it, but save money by doing it, when nobody had ever done it before?
Similarly, electric cars were far from new. Nobody seemed much inclined to build one that was actually a luxury car, instead of a toy for engineer-types who could put up with driving weird things. Any of the big manufacturers could have done it, and easily absorbed the losses if it failed, but none did. Elon made a wild bet on that, making a company that made nothing else, so the whole thing would go down the tubes if the idea flopped. Instead it seems to have worked. Although it seems to be harder than he anticipated, and maybe outside his skillset, to run an organization that does real mass-production.