Absurdity in the lack of testing. I know it probably wasn't the fault of the implementers, but the management above them, but gosh, "move fast and break [people]" is not how financial software should be made.

There was pre-existing systems, could have just ran it side-by-side to see if it agreed with the old methods.

With how completely avoidable this result was, with people raising flags all the way through, I feel that the only conclusion is harming citizens must have been part of the intention.