I have no way of knowing whether the stage's resemblance to the collar tabs of the
7th SS Volunteer Mountain Division Prinz Eugen is intentional or not, or why they chose to commemorate that SS division in particular, if it is intentional, though if it is intentional I find the course of events that led to their selecting that design, and then persuading the design company to lie about it, and take responsibility by issuing a press statement to a left-wing Jewish news organisation, of all places, so without further evidence I want to leave that alone because it suggests serious dishonesty on the part of the owner of Design Foundry and her employees.
It seems to me unlikely, given what we know of her, that she would have anything to with such a plan, so I would need more evidence than simple supposition before I'm prepared to entertain the idea at all seriously, though I accept it's a theoretical possibility.
But I just don't see what depends on all this -- we know what Trump and his supporters are like, which is why it wouldn't surprise us if they did choose the shape deliberately, but I don't see how it being their deliberate decision to base the shape of the stage on a Nazi symbol makes them any worse than we already know they are, from their own words and actions.