Musk was always very 'optimistic' about Tesla goals and timeline estimates. That's fine (I guess) when you're a small company trying to achieve a major breakthrough. And they did actually deliver and started to mass produce EV cars - absolutely impressive result.
But in the process, Musk also started to promise more and more impossible things, on a bigger and bigger scale - FSD (almost 10 years ?), Robotaxis (!), Tesla's cars as 'appreciating assets', Boring Company, recently Optimus, AI, Tesla Semi, Cybertruck. Infinite demand that he claimed on investors earning call (he knew the real numbers) ?
The scale of optimism varies of course here. Tesla Semi for example ? Announced 6 years ago, officially started deliveries 1 year ago. In reality, those are prototype trucks, with specs and price being kept secret.
Another interesting one is the deal with Hertz - in October 2021, they announced a deal with Tesla, in which they supposedly bought 100k Teslas. Tesla stock skyrocketed (something like +50% in 3 weeks), to hit its all time high share price beginning of November 2021. It turns out (as announced by Hertz last week) that they only bought 35k Tesla's so far.
It's fine to say with huge optimism you're tackling a big problem when you're a 50 persons startup. It's another thing to say that you are in the process of building and close to delivering them as a huge public company, whose valuation is higher than 10 next competitors combined (when said competitors are doing >x10 sales).
And it's an entirely different thing, when the main character of the story, sells almost $40B of stock (!!!) at the peak of the hype he created. To give some perspective, $40B is the entire valuation of Ford, or GM. And he sold with excellent timing too. Remember this Hertz story - October 2021, then shares hit 400$ (all time high) beginning November 2021. Elon Musk starts selling on 8 November 2021.