Most news organization started showing Trump campaign speeches because they got ratings. A lot of the ratings at first were from people outraged and incredulous at his rhetoric. The net result was that most news organizations gave Trump undeserved exposure. The extra exposure ended up putting him as the Republican nominee and eventually as the President. The press, in seeking ratings, got involved in the political process. They are not supposed to do that. After Trump was elected, Fox News (which actually is registered as an entertainment network so they won’t be subject to regulations that apply to news networks) made some attempts at calling Donald Trump on some of his lies and questionable behavior. What they found was they were swiftly punished with poor ratings every time they did that.
Fox News chose to support Trump to make money. They knew they should not have done it, but they weren’t really news, and they wanted to stay in business, so they kept doing it.
Trump meanwhile criticized Fox News openly and off-ramped his supporters to more radical and biased news sources such as The Blaze, Breitbart and The Drudge Report. When Fox News saw that it was likely that Trump would lose, they made a business decision to keep themselves in business by distancing themselves from someone that has a lot of liabilities. It seems likely that there were a lot of people around Trump, and including Trump himself, that still will be charged and convicted of criminal activities. Fox News hopes to make money and maintain ratings by covering all of the court cases that will surely follow. It is better for them now to not be seen as an enabler of a person who will surely end up exposed for fraud, bankrupt, and morally indecent. And it will probably work because Trump supporters either have very short memories or a lot of cognitive dissonance and they can be convinced that Fox was never a supporter or enabler of Trump.