> What’s really going on here? Why do banks completely ignore the terms customers agreed to when they subscribed, or even in cases where the claims are obviously false? And why aren’t customers required to provide any proof at all?

they have a banking relationship with their client, and none whatsoever with you

if they decline the chargeback they then take on a load of risk (they might lose their client, they might get reported to the regulator, they might be sued by their client and then stuck with the bill)

but if they just pass it on then you take all the pain

not surprising at all given the structure of how credit card payments work