Because the Decision Desk was smart enough to calculate that Trump had no hope of getting the votes he needed to take Arizona since the lead wasn't where it needed to be before the outstanding votes of Maricopa and Pima.
Nate Silver is jealous that he didn't get to call the Election and someone did things better using traditional means. That's all.The night of the election, Nate Silver did think Fox should retract calling the state because it seemed possible at that point for absentee ballots to give Trump the win.
The world is not wired to his rear end.
Fox called it not for "the good for the country" but because it made sense with their calculations just as it did in 2012 when they called Ohio or in 2018 when they called the "blue wave".It was good for the country that Fox News made the announcement, because it prevented Trump from being taken seriously when he lied.