I wonder if it would have gone differently if Jack hadn't been so smug when he showed up, if he hadn't called it "the accident," if he'd been as sorry as he was when he was talking to Hallucifer. But Sam was his best chance, and I think he lost Sam by being so cold instead of regretful. It made Sam think, even if for a moment, that he was too far gone - I mean, look how frightened he was when he reached out to touch his shoulder.