I think google should be held accountable for not removing a malicious app from their app store within a reasonable amount of time, but I'm less sure that Google should be on the hook for the money scammers take. Google can and should do a lot more to prevent malicious apps on their platform, and they should be required to respond quickly when the ones they failed to detect are reported to them, but a play store that only allowed/contained apps that Google was 100% confident could never be used to scam another person wouldn't be very useful.