It’s also possible that Uncle himself may have a history with drug/alcohol use that he was able to control or stop (some folks get frightened by their increasing seeking behavior early on in what would have become an addiction, and quit right then), without it becoming family knowledge. If that’s the case, he may find being around addicts personally triggering. Or he may have a history with abuse that leads him to find being around lying/manipulation personally triggering. It sounds like he pulled away when the lying and stealing was first coming to light, so either of those are also possibilities. If either of those are the case, he tried once to reach out, the experience felt as awful as he feared, and he’s kept his distance since.

It’s probably most likely that he’s just a “fool me once, shame on you, fool me again” kind of person and doesn’t want to risk comtact. That’s completely reasonable. But I wouldn’t want to discount the possibility that addiction is personally impossible for him to be around due to his own history. (I think codependence in this case is unlikely because the uncle pulled away as soon as shit started going south; usually people who are codependenf with addicts stay in the trenches with them.)