Have you seen what he posts on his social media accounts? It is full of fascist, racist, conspiracy content. It is almost certain that he knows how a Nazi salute looks like and that it was two of them.
In case anyone sees this... this is true. I've never actually seen Elon himself post something blatantly racist.
Instead he'll wait till someone else like Marjorie Taylor Greene posts something like "jewish space lasers are responsible for California fires" and he'll retweet "close".
He does this so often, it's like he wants to be technically innocent of wrongdoing, but he's associating with all the bad actors.
Nor does he talk "normally", so that's why I don't put much faith in the assumption that he was thinking that he was doing a Nazi salute.