Google's history with their payment apps/platform is almost as convoluted as their history with message apps/platforms. I swear they have gone back and forth on Android Pay/Google Wallet/Google Pay a half dozen times.
I forgot where it was mentioned [1] that the mess comes from a poor management of international feature list. In particular, Google wanted it to be successful in India. But the prior app was designed with USA sensibilities and requirements. Such as, oh, requiring an email and Google account! The thought was that this wouldn't fly in India, and it had to work with just a phone number. I'm sure there were perverse/cros…
As a part of that initiative you had manufacturers building super low-cost Android smartphones that came preloaded with Google apps and people could put a SIM card in. The backing system of GPay in India called UPI works similarly so this app could never have that second layer of auth as a mandatory wrapper and spread where Google wanted it to spread.
Those decisions gave them 200M users on the app in the country.