Why do you think Google is best. HAve a look at Daimler, Bosch, BMW, etc.

It appears to me Google just gets more attention. I doubt however that, generally speaking, the amount of attention has anything to do with the real level of achievements. However, it's not exactly my field, just a feeling: Convince me of the opposite, if you like.

I feel like adding that a secondary aspect is that there is more to making a mass-produced car than getting the autonomous driving right. Assuming that Google wants to build such a car (not sure whether this is still their intention), I guess it would be interesting for them to watch how Tesla will cope with getting their first volume model into production.