I have no idea if Elon really is a Nazi at heart, I don't follow him closely enough to be able to make any such judgement. But it honestly looks more like a "Fuck yeah!" gesture than anything else to me, like you might see in a touchdown celebration move, but clearly I'm in the minority on that one.
No need to make it an argument. It's just the impression that I got. I could be wrong about the football thing too for all I know, its just what it reminded me of.