He’s not naturally charming in front of the camera and he doesn’t care.
I would phrase that slightly differently - more like being a media personality is not important to him, rather than he doesn't care what people think of him.
His manner seems to me to reflect his upbringing - born to a moderately wealthy family of expat Brits in Africa, both his brothers were sent to public school in England but the money ran out before it was his turn. He's a posh boy
manqué. Instead he fell in with David Kinjah and learned a) some humility, and b) how to ride a bike.
Just think - he could have turned out like David Cameron or Jeremy Clarkson instead.