We'd already noticed it yesterday when it was announced Reagan died... the other news channels were showing Iran/Contra footage and talking about Star Wars and about the timing of the hostage release from Iran. Even a couple of the FOX anchors (Shep, as mentioned by others and you) were walking really close to the edge, questioning his mental capacity at the end of his Presidency. They have no shame and always want to gossip.
If I were Shepard Smith, I'd be really careful about questioning anybody else's mental glitches. As the saying goes, there's probably a good number of people who'd rather give him a curb job than a...block party.