Because the product is better than anything else on the market, and the lies are fairly benign and easily excused as brash optimism.
If it was the choice between Musk's offering and a car from a bland manufacturer without an asshole at the helm that still did everything the Tesla did? Sure, I'd drive the Mercedes or Cadillac or whatever. But there just is no such car. What I want is a Tesla, period.
I think most people know what Elon Musk is like. He promises a lot. He delivers a lot too. But his promises are always optimistic and running ahead of delivery. That's especially true on timelines, but true on other matters like functions or capabilities as well. I think most people take that into account when processing his statements, and mentally subtract some of the over-optimism from them.