I don’t know much about trading stock, but I do know SpaceX is not a publicly traded company. That means his buyers for those shares are super limited, so each potential buyer would likely be super wealthy and would have more say over the company than any one individual in the horde of public buyers that would buy up the Tesla stock. Plus, him needing to divest from Tesla might actually drive Tesla stock up a little (eventually), since he won’t have as much control of the company as he did before. It seems he would still be the largest shareholder after the selloff, but this would close the gap between him and the next largest shareholder. He owns over 3x more Tesla stock than the next largest shareholder.