Speaking confidence has nothing to do with lying or telling the truth. Go back 20 years ago and look at a Biden speech and compare it to today. Hell, go back 4 years ago to the last Biden v Trump debates.
Biden isn’t half the capable public speaker he was before. He mumbles and gets lost. He sounds unsure.
Trump doesn’t care if what he’s saying truth or not, he just says things with the conviction of a conman.