There was at least one previous Black Panther who knew how to levitate. I don't see T'Challa knowing how to do that without accessing that previous Black Panther's knowledge of how to levitate. And I'm not certain we know for sure that T'Challa was the smartest of all Black Panthers so far. There could have been other previous Black Panthers that also were geniuses in their time periods. Weren't there like 10,000 years worth of Black Panthers? A LOT of them could have been extremely smart.