One could argue it wasn't "augmented reality" at all. I doubt cell phones have the power to take their camera feed in, do actual computer vision to analyze the (arbitrary) world [1], and then overlay anything with any interesting intelligence at all. (Even if you can scrape together the specs to say that high end phones might be able to do nontrivial work, I wouldn't be surprised you hit problems like internal hardware bandwidths and such. Even before we discuss battery, which Pokemon Go certainly chewed down pretty well even without complex analysis.) Pokemon Go was just a character laid over the camera with no intelligence.

[1]: I have to qualify this because the 3DS can do some things with certain prepared cards, and cell phones nowadays outclass the 3DS quite handily. But doing any sort of analysis without such hints, which certainly have not taken off, is way harder. https://www.youtube.com/results?search_query=3ds+augmented+r...