Comment by virodoran

Perhaps, perhaps not - I have my theories, but is that not what you meant when you said Pokemon Go was built on the same engine as Ingress?

I do think it wasn't until after Pokemon Go launched and they saw the success of it, that they shifted focus to be more of a platform for these types of experiences (see Niantic Lightship). Additionally, I think Unity offered them the opportunity to integrate with ARCore and collect much more detailed data than they would've ever been able to do on the old Ingress engine. In fact, I expect a significant chunk of ARCore functionality was added specifically thanks to Niantic and Unity (in fact, you see Unity mentioned all over the Google Developer docs for it).