Newspapers don’t make much money any more (though in the 90s they made returns in the teens regularly.) What they do still have, though, is influence and power. Even though newspapers don’t have the reach television does, they determine the stories of the day—they control the news cycle more than any other part of the media. More than that, newspapers are intelligence bureaus. Rupert Murdoch, no fool, would spend hours on the phone with beat reporters, picking their brains.
Power leads to money. Amazon is under what Bezos must consider attack (as in making Amazon pay sales taxes), and he needs influence, power and intelligence in DC. The Washington Post, at 250 million, is an absolute steal, even if it loses money every day.