Autonomous driving to me seems a lot like the domain of robotic crowd navigation, and the crowd navigation research seems to show us that most of the methods suspected in-use by AV programs tend to fall apart under trivial thresholds of uncertainty/congestion. So, I'm less surprised that Uber didn't make much fundamental progress here, and more surprised that anybody else has done better.

edit: I say this as someone who very much wants to see this class of science & technology succeed, but I often wonder if we're 2 or 3 Fields Medals away from really getting fundamentally closer to success.