Voluntarily transferring money is very different from having it stolen. The bank should protect your money while holding it from theft. They can't protect you from your own decisions on how to use your money.
They voluntarily accepted a contract wherein they would transfer money in exchange for receiving a bicycle. No bicycle was received, so this voluntary decision does not mean that the money transfer was voluntary. They did not accept a contract wherein they would transfer money in exchange for nothing. Since they did not accept this contract, this does not make the money transfer be voluntary.
Being a victim of fraud is not "voluntary" in any meaningful way.
> this voluntary decision does not mean that the money transfer was voluntary
Voluntary or not is a red herring. The word this discussion is looking for is authorized.
The transfer was authorized by the account holder. They were defrauded. But when they made the transfer, then intended to do so. (The situation is murkier with credit card transactions, at least in America, because they chose to accept a role in dispute resolution.)
The $625mm drained out of Axie's account wasn't authorized by Sky Mavis. That's a different type of fraud than being ripped off.
In the old American paper check system there was an important but subtle distinction between "fraud in the making" and "fraud in the inducement". If a criminal stole your checkbook and forged a check then an intermediary (like a bank or a grocery store) which cashed a stolen check could be on the hook for the money--if you protested to your bank the transaction could be reversed. However if the criminal simply induced you to write them a valid check (e.g. as payment for a non-existent bicycle) then any intermediary that cashed the check is not on the hook, and the only recourse is to get the money back from the criminal.
