If he did it once, it would have been an extremely low but still non-zero chance that it wasn’t a Nazi salute.

He did it twice though, it’s now firmly a 0% chance of any kind of coincidence, misunderstanding, etc.

Thus far he’s made no comment, not even to deny the Nazi intent.
No apology, no backtrack, no denial, he did it twice.
It was exactly what it appeared to be and nothing less.