Trump is like a character in a TV show who's characterization is 'petty'; you see that character always one-upping, always trying to get the last word in and you think, "yeah, I guess this makes for decent television and it moves the plot along, but nobody is actually that petty. People just don't behave like that."
but this guy, our big wet former president. He actually is television petty for real. McDonald's is his thing. It's what he's known for, he knows the menu better than the cashiers (allegedly). So when he hears Harris worked at a McDonald's at one point in her life, well. This Means War. He has to prove he's the most McDonald's candidate.
And I get this beautiful jpeg. look at it. he looks miserable. the guy in the back office looks pissed. They had to drag a camera and a bunch of secret service guys into this cramped little kitchen that barely has room for two people to pass one another. Amazing.