@Syanalassa
It's actually pretty simple, imagine if the pope was caught committing a crime against the church or a soldier commited war crimes, the hero essentially was given the equivalent of favor of the gods, to betray said gods trust and get his status removed would be the equivalent of angering the heavens, so it's entirely possible they executed him simply because his betrayal could bring hardship later, plus being able to see if someone is evil probably helps tons, if you could tell someone was a bandit immediately then in the past most soldiers would attack on sight, no questions asked, i think the bigger question is why he'd go back to the human leaders in the first place instead of flee, considering the gods basically marked him for death.