The ways it set up its board and Mr. Musk’s pay appear to benefit him at the expense of other shareholders, corporate governance experts said.

As SpaceX prepares to go public, Mr. Musk has proposed moonshots that differ from the company’s original aim of reaching Mars.

A verified account with the @elonmusk handle also recently showed up on Instagram, as the billionaire prepares to take his rocket company SpaceX public.

The Tesla and SpaceX chief has told his followers that they will live in a world where robots will take care of every need and…