Well, here's another unsettling theory. He's no doubt been under a huge amount of emotional strain lately for all the obvious reasons. Maybe this is sort of his way of acting out -- a kind of "Oh, f'ck it all!" response, almost semi-self-destructive. I mean, he's not just underdressed for an awards ceremony. He's not even committing a small rebellious act, like wearing Converse high-tops with a tuxedo. He's out-and-out absurdly dressed.
All the outfits we've snarked about in the past, the Smurf hat, the too-small jackets, the red sunglasses, etc., all seem like sincere choices that just happened to be unflattering. But this! This is like giving the finger to all those really-dressed-up people on the red carpet with him.
If it's a self-destructive kind of act, I feel bad for him. But the bright side is that there are far worse ways to self-destruct than wearing red-striped socks.