Jill knew the state of her husband before announcing a run for president. She knew moments like this would happen. For some reason, she thought the dignity of her husband didn't add up to whatever she gets out of this trainwreck.
He has no idea what is going on here. He has no idea what "Let's go Brandon" has come to mean. The reactions he has at those rare times a reporter asks him a question that reveals widespread disapproval of his performance probably indicate that Joe is shileded from many things. And then there's the question of how much he is told that he actually remembers.