[mikejb]

I'd say the breakthrough term was not the ideal word choice - it's more that technological advances passed a threshold:

For VR, a lot was advances in (affordable) processing power (latency causes significant issues in VR), and screen (manufacturing) technology (i.e. pricing improvements).

For self-driving, it's again processing power (with the focus on the ratio between computation power and power consumption/size), but also the advances in technologies like Lidar, as well as advances in theoretical research (and better understanding) of machine learning.