Because Hilary was such a shitty candidate she lost to Trump?
And yes, Kasich lost in the primaries to Trump and Cruz. But come general election time Kasich would have had those votes, plus many of the reasonable people in the middle who either didn’t vote or bit the bullet and voted for Hilary to avoid Trump
Also, DNC was telling the media to do what they could to get either Trump or Cruz nominated as the Dems felt they were the easiest to defeat. Media did that, hence the focus on the spectacle rather that actually showing the candidates policies and strength