Google's Sergey Brin predicted driverless cars by 2017.[2]
BMW predicted we'd have driverless cars by 2020.[3]
Supposedly sober industry analysts predicted 2019.[4]
It's also worth pointing out that many of Elon's predictions were not predictions of a finished product, but rather predicting when Tesla would have a system "capable" of self driving, not necessarily a system capable of driving consistently and reliably. (In much the same way, I am capable of hitting a target with a crossbow, but not consistently and reliably.)
To be clear, I'm not defending Musk's predictions, only pointing out that such predictions were widespread and Musk was just one of many, many, many people who turned out to be wrong.
[1] https://www.businessinsider.com/travis-kalanick-interview-on...
[2] https://www.theregister.com/2012/09/25/google_automatic_cars...
[3] https://www.theguardian.com/technology/2015/sep/13/self-driv...
[4] https://www.businessinsider.com/report-10-million-self-drivi...