The autonomous driving question is an interesting one. It's probably some combination of techno-optimism, naive extrapolation of deep learning advances over a fairly short period of time, and--yes--at least some degree of a massive game of topper because everyone else was feeding at the funding trough and saying things were right around the corner. How much of each doubtless depends on the person.

And a lot of other people listened to the vocal "experts" and assumed that they must know what they're talking about.