Because unlike much of the GOP and the RATS, he is not stupid.
More to the point, the once boot licking, Biden fawning media is working so hard are trashing and destroying Biden that they uncharacteristically seem to have forgotten all about destroying Trump.
He is allowing them to eat their own and he has risen above the nastiness against an old white guy with Alzheimer’s who happeneds to be president. The blood is in the water and the sharks are his own party and admininstration