Well, how can it not be mainstream if it adds to what Pokemon GO offers.
The reason is not in the Pokemon. This is a game that allows you to make money at the same time. Such projects in the field of cryptocurrency are just starting to appear. Pay attention also to cryptokitties - the idea is absurd, but how viral!
I believe that anything that could be described as "cute" can get popular without an actual purpose.
Speaking of Pokemon, you can't really choose to not compare this project to Pokemon GO because for newcomers the idea of a game with similar flow to Pokemon GO would sound a lot more compelling than "a project that uses augmented reality instead of GPU mining".
in any case, the creators themselves say that they chose the concept of Pokemon. I do not understand why these arguments.