I think that Trump said McCain was a hero because he was captured and that Trump liked people who weren't captured. Regardless it no doubt made McCain an permanent enemy who waited patiently until he could get his revenge. And he did with the Obamacare vote.
McCain started it when he called Trump supporters “crazies” in 2016.
He also handled that fake dossier, he was the one that turned it over. McCain was trash.