For the younger folks: Kerry got some seriously badass medals for his military service in Vietnam. People who had been on the same boat as he did, but at a different time, worked with the Republican party to claim that he hadn’t really done what he did. The press ate this up, and distributed it widely, costing him public support and likely the election.
I think people operate on a belief of fairness that obviously does not actually apply in real life. Bush was a draft dodging rich kid and Kerry actually got injured and awarded for heroism, but media manipulation made Kerry’s service an issue. That Trump is a big sack of lumpy turds isn’t going to save us from hypocritical false attacks being drummed up because the media wants excitement.