tl;dr Why are electric cars harder to build than rockets: 1) they're not. 2) a different question: why an electric car company may be more difficult to succee

tl;dr Why are electric cars harder to build than rockets: 1) they're not. 2) a different question: why an electric car company may be more difficult to succeed than a rocket company, is because the former competes with a trillion dollar internal combustion engine industry with more than a billion drivers of vehicles, deep-pocketed incumbents, and the latter has relatively little competition.