The problem here is the assumption that one account pulls down tens of thousands of dollars. There's nothing keeping the scammers from spreading the ebooks across multiple accounts, and getting $1000 an account across 70 accounts. That's much harder to track by the method suggested due to both the sheer number or accounts and the much smaller payout per account.
I think this is the crux of it. Spam is a lot harder to track than most people realize. Written spam is still a thing in email 30 years later. There's a solution to this but I assume it's a cat and mouse game. To think Amazon just doesn't care about the authors getting scammed is foolish. Without a lot of human involvement this is a very big problem space. One could accuse the program of being poorly thought out but I think that the idea that no one cares about the issue is disingenuous.