He knows he was never legally responsible for his mother’s bills.
He was lying and using his dead mother’s cancer and evil insurance companies to play on people’s sympathies, so that they would identify with him. So many people are so ignorant about how insurance works that he knew he could get away with it. How many people out there actually believe that when their mother dies they will have to pay all of those hospital bills? Are they frightened into believing that this this will happen to them, like they wrongfully believe it did to Obama, and thus they support Obamacare?
Barack has a gift doncha know? His gift is the ability to make up stories to play to the particular audience in his presence. During the Campaign, those audiences were made up of his prime constituencies, Bigots and Morons.