As a society, we have arbitrarily chosen to stigmatize certain things tied to the Nazis. For example: the toothbrush mustache is pretty much banned because it will be taken as an ode to Hitler even though it was a popular mustache at the time that many people wore, including Charlie Chaplin. One of those things is a Nazi salute. The Nazi salute is relatively unique, but it's not like someone having a tattoo of a swastika. There are many gestures that have people put their hand to their heart and then wave. It's not out of the realm of possibility someone could stumble into doing such a gesture.
Again, it's not like getting a swastika tattoo or yelling sieg heil. At the end of the day, I believe in giving people the benefit of the doubt. Most people are not Nazis or hateful. I've seen this before where people have Eagle tattoos and people associate it with Nazis, or some weird discourse around the number '88' which was one of the more laughable ones. If I'm to put odds on it I think it's far more likely people are going to disingenuously try to go after someone they don't like than it is Elon Musk was trying to do a Nazi salute. But we can believe whatever we want, the reality is none of us know, and I think it's both counterproductive and a waste of time to get so worked up about something no one can confirm to be true.
This reminds me of the ok symbol from a few years back and people getting into trouble and even being fired for it. People would accuse them of being white supremacists, and then people would go no, that's not what I was trying to do and people were going "Yes you were." At that point there can't be any dialogue. If you can't take someone's word for something, then there's nowhere to go from that point. You can either accept the answer and move on or continue to be a stickler about it, and whatever choice is everyone's right, but I think objectively there is one path that is more productive than the other. What does being pissed at Elon over this even accomplish anyway other than make someone feel good about themselves?