I agree. But it's not just that his management skills, such as they are, are not transferable to the presidency. It's that his personality traits--his arrogance, combativeness, hair-trigger temper and disinclination to heed wiser counsel--all but ensure that he'll be spending his entire time in office setting endless fires that his put-upon staff will labour mightily and often fecklessly to extinguish. (Will it continue to be a hot mess? Yes!)
Also--I don't think he's nearly as smart or as shrewd as he thinks he is. He's gotten a lot of mileage out of being a billionaire because, as per that line in the song "If I Were a Rich Man," "when you're rich they think you really know."