Yeah I need more info too, heh. It was definitely a stock Trump utterance you'd use to mock him by the time he was president, whether he himself ever actually used it or not.

He's definitely made using, "Sad!" as an ending to a comment a thing. I can't attribute it to him entirely honestly because I think it's such a short, common utterance.

I feel like he popularlized it but I'm pretty sure my dad has been going, "Sad!" after a lot of my antics my whole life lol