Branded credit cards bring in a surprising amount of money – the Apple credit card is projected to earn Apple $1 billion annually with very little risk. I think it’s notable that this is a debit card and not a credit card – a debit card charges purchases against a checking account (in other words, money is there before you make your purchase) while credit card purchases are essentially a short term loan. By making it a debit card, Google reduces their risk by requiring that consumers already have money in their checking accounts to charge against. Additionally, Google and its partner bank earn interest on that checking account’s balance.
This is another way of diversifying Google’s income stream away from Ads; I wouldn’t be surprised if we see the Google credit link to benefits on other Google properties – for example, free or discounted YouTube premium, discounted Google Home devices, etc.