Ever read the The Selfish Gene book? I do believe Elon wants to help save humanity, at the same time his motives can be partly selfish. He quite clearly knows that if freedom of speech is lost then the totalitarians have won, and he'll lost freedom as well - and he'll be "forced" then to aid the totalitarians in whatever they do, even if knowing they're genocidal, etc; I suspect he'd refuse to work in such conditions but who knows what blackmail - like threats of torturing or killing his children, etc - could be tried against him.
And yeah, Sam cares about money and some other things, it seems.