There's also the issue of how hard it is to select the line of code (API call) that does the job (because the API surface is huge), which is nearly invisible attribute.
Mathematica is famous for being incredibly powerful with low custom coding, but also very hard to find the API call that does the precise thing you need.
IMHO, credit should always go to Alex Krizhevsky for the rapid spread of deep learning. He has shown us it was possible. Even without Tensorflow and PyTorch, we will be fine with Caffe, torch, mxnet or Julia.
By way of analogy, David Heinemeier Hansson didn't invent the webapp or even the MVC design pattern. But Ruby on Rails did change the way webapps were built, and enabled a bunch of stuff that wouldn't have been possible otherwise (or, at least, would've taken longer and been more expensive). Lots of websites were built because of Ruby on Rails that probably wouldn't have been built otherwise, even if people would've kept on doing the web thing regardless. We can say the same thing about lisps, about linux, and about a lot of other software infrastructure.
Any high schooler who's capable of learning python and can afford a gaming desktop can build and train a neural network. That's pretty amazing, and definitely wouldn't be the case without computation graph frameworks.
I've never worked for Google or with Jeff, and I'm not a huge fan of the ad tech industry, although I don't understand why either of those things should matter.
If you want to know what the next hot thing in software engineering will be, just pay attention to whatever Jeff Dean is doing.