I think from the original DARPA challenges most researchers knew that while self driving is possible or more correctly "a promising direction", but its application to the realworld and its robustness was a far larger barrier back then.

We have the advantage of retrospect when looking at these claims which now may seem more possible then before due to our better understanding of the difficulties and technologies to address them.

I think many people confuse their excitement for the promise of having self driving cars and the actual technical and political barriers that still need to be addressed to bring this to reality (ranging from robustness, infinite number of edge cases, perception, insurance, or public policies).