He may be very happy just being a spoiler candidate that sucks off enough Republican votes to make them lose the next election.

I hear you, but that sort of detail is probably below the waterline for an interesting HN conversation.

Someone else filed the application for him, and that application includes a fresh email address for this purpose. There is no reason to deduce from this that Musk had anything to do with choosing Protonmail, that he intends to read the mail directed there, that he is otherwise a Protonmail user, etc., etc.