Fox News was established in 1996 by head of Newscorp, Rupert Murdoch. He appointed former Nixon, Reagan, and GHW Bush media consultant Roger Ailes as its president.
It is often claimed that Fox was set up to redress the balance of an overly liberal media in the US. If this is the case, Fox 'redresses' by taking a pro-conservative stance and labelling it 'fair and balanced'. What legitimate news needs to trumpet its fairness? Surely it should be implied.
I believe Murdoch simply saw a niche in the market and exploited it to best advantage. It was a business move for him as much as a political one.