> His great accomplishments were having a multi-decade vision of how to build an AI and actually keeping the vision alive for so long. You have to be charismatic and convincing to do that.
Taking a big shot at doing something great can indeed by praiseworthy even if in retrospect it turns out to have been a dead end. For one thing because the discovery that a promising seeming avenue is in fact non-viable is often also a very important discovery. Nonetheless, I don't think burning 2000 (highly skilled) man-years and untold millions on a multi-decade vision is automatically an accomplishment or praiseworthy. Quite the opposite, in fact, if it's all snake-oil -- you basically killed several lifetimes worth of meaningful contributions to the world. I won't make the claim that Lenat was a snake-oil salesman rather than a legitimate visionary (I lack sufficient familiarity with Lenat's work for sweeping pronouncements).
However, one thing I will say is that I really strongly get the impression that many people here are so caught up with Lenat's charm and smarts and his appeal as some tragic romantic hero in a doomed quest for his white whale (and probably also as a convenient emblem for the final demise of the symbolic AI area) that the actual substance of his work seems to take on a secondary role. That seems a shame, especially if one is still trying to draw conclusions about what the apparent failure of his vision actually signifies.