The reason Biden did not personally tell the cabinet is he does not even know who the hell his cabinet members are other than his Defense Secretary who he referred to as the black one the other day because he had no clue what his name was.
I’m hearing reports that Biden was asked to tell his cabinet himself, so he went to the kitchen, opened up his pantry and starting talking. After a few minutes of that, they decided it was best to have his Chief of Staff tell the cabinet for him.