Are you familiar with how TV revenue works? Here's a hint: ratings. Covering Donald brought higher ratings than whatever drivel they would have otherwise aired. They covered him because it drove ratings, not because they wanted to. Same for every other media organization. They simply had no choice but to cover him, he moved the ratings needle.
They have tons of pundits, most of them lefties. Why not hire someone who actually knows the Trump campaign as a pundit?
Lets face it, there was very little discussion about policies in this election, from either party. The viewers simply didn't care about the policies. It came down to which of these two jackasses do you like the least. Trump's ugly comments vs illary and her lies, corruption and email problem. Kind of hard to ignore a topic that could have landed the candidate in jail