I didn't log in, am not a member, just closed the log in thing to see the video.
Why would you do that? You can look at instagram videos while you're logged in to IHub or anything else. It'll just open a new tab.
But I see from the video that there're a whole bunch of Saudi military types, and they all saluted. There was still no reason for Trump to do so, but I'm sure it made him feel delightfully important.