I can't prove it, but she IS Secretary of State and it would be one heck of a social faux pas if she didn't invite him.
I think they had an 'arrangement'.
OTOH, Michelle would have sucked the oxygen out of the wedding.
I think it is totally intentional. He’s garbage and she will take the gloves off this time. watch to see when see resigns for so reason and then the press starts backing her. He’s doomed as a prez.