I don't know if Fox style news is caused by their impotency at the polls or is causing it. In any case, it's hard to believe that it's helped. It has done wonders for Rupert Murdoch and Roger Ailes' net worth but it's not obvious that it's done much for the Republican Party.
In any case, Fox is a specific instance of a wider trend. Media has become increasingly sophisticated at driving up ratings. It does this by finding the most alarming news or possibilities available from among all the things happening on 7 continents, in 200 countries, among 7 billion people. With that much to select from, there's always something. Always.
Then the media puzzles over why voters are increasingly frightened and angry.