It's funny to use "the market value of all taxi companies combined" as a proxy for how valuable the self-driving market will be, because that's exactly the reasoning that led people to underestimate Uber. The market value of all taxi companies combined was pretty small when Uber started.

That said, you could be right! Maybe self-driving will never be worth more than that. It's really hard to tell what business models will be like in the future. But this is the cultural mismatch, it seemed like GM leadership did not want to be in a risky business where they were betting billions of dollars on the success of self-driving. Clearly, to some people, that seemed like a really good bet to make. Time will tell.