As missiles rain down on the Middle East, Trey Yingst fires off salvos of news from his smartphone. The 32-year-old chief foreign correspondent of Fox News dons a flak jacket and stands on a Tel Aviv balcony to file reports several times a day. His main audience is on cable. But Mr Yingst has cultivated another set of viewers on TikTok, where he posts bulletins to 1m followers. He is such a prolific poster that viewers sometimes enquire after his safety when he has been offline for more than a few hours. Fox is the undisputed king of American  TV  news. Long the tribune of conservative America, it has become so widely watched that it is also the most popular cable news channel among Democrats. As well as out-rating  CNN  and  MS NOW , its main cable rivals, it sometimes beats even broadcast outlets like  CBS  News. Donald Trump’s return to the White House has brought back advertisers, who are now less likely to see Fox as brand-threateningly right-wing.…