I&#x27;m betting that they finally solved the scalability problems with headless WebKit.  Google&#x27;s been able to index JS since about 2010, but when I left in 2014, you couldn&#x27;t rely on this for anything but the extreme head of the site distribution because they could only run WebKit&#x2F;V8 on a limited subset of sites with the resources they had available.  Either they got a whole bunch more machines devoted to indexing or they figured out how to speed it up significantly.