Olly is a d**k. Even before the events of the finale, he was a d**k. Yes, his village was ransacked by wildlings, and they killed his parents, but Jon Snow was nothing but good to him. He killed Ygritte during the Battle of Castle Black, but is later made a full member of the Nights Watch, and Jon names him as his personal steward - the same position Jon held under Commander Mormont. He is extremely prejudiced against the wildlings, and cannot understand why Jon would risk his life and those of other brothers in order to save them, and those feelings are shown to be building throughout season 5. Despite all this, Jon still trusts him at the end when he comes running to say a wildling has word of his Uncle Benjen. It was, as we know now, all part of a mutiny, luring him into a trap so that they could kill him, and it is Olly who tearfully delivers the final blow for the Watch. F**k Olly.