“I’m sure it would have been very awkward for them not to attend, but that’s it.”
It might have been a lot more than awkward. We don’t know how Trump would have reacted. Ivanka seems to have a very good relationship with him, but that might be because she makes sure to do what he wants. Maybe that’s where the pikuach nefesh issue came in.
We also don’t know what the repercussions would have been for Israel and the Yidden. The Rav issuing the Psak probably took all this into account. There are also probably many factors involved that we are unawared of both in terms of the situation and in terms of the halachos involved. I don’t think that anyone here is qualified to posken on the situation.