It's only lying if he doesn't believe it. And he demonstrably does. He has a whole division at Tesla designing a humanoid robot for mass production in the next few years on the assumption that the AI will be ready by then. He keeps removing sensors from their cars on the assumption that AI can replace them in a few months' time. He started a brain implant company with basically no near term market potential because he believes it will be important for interfacing with the upcoming AIs. If he didn't believe his own statements about AI he wouldn't be doing those things. It may be borderline delusional, but that's not the same thing as lying.

Consider that in the past plenty of other people in the industry have underestimated things that he's overestimated, such as the potential for reusable rockets, and the timeline for electric cars becoming viable, and the timeline for low-cost phased array antennas to support Starlink. And those have been incredible success stories for him, despite his initial overestimation, which really was overestimation, that many called stupid at the time, with some justification. And AI may yet turn out that way too. Even if he's wildly optimistic about timelines, he may still end up closer to correct than the conservative establishment in the industry which has a very strong status quo bias, like with disposable rockets and internal combustion engines.