My first inclination was to think, of course, he wants to allow space for Americans to honor the officers who died or were maimed as the rabid Republican mob attempted to overthrow US democracy.
But no.

That would be about the stupidest thing to think, the least likely authentic reason.
So, putting on my "Republican RatF*cker Receiver" I'm able to totally trash my Pollyanna Fantasy life, and picture something more appropriately sinister, more Republican you would have to say.
Maybe the Slobfather, as he is unaffectionaly known by decent folk, knows some shit is up with the BOYS and their ILK on 1/6, and realizes if he's on the toob blathering his usual Republican lies, he'll get blamed for it.
He wants to dodge responsibility for the shitpot he's always stirring. He always dodges responsibility.
amirite?