who is responsible?
The scammers.
Who have spent - in various incarnations - centuries learning how to con people out of their money. If someone falls for it, is it their fault? If a bank has reason to believe that they're giving money to the right person, and they're not, is it their fault?
As it happens, I moved a lot of money from the UK to a foreign account recently. My bank required me to be there in person to approve it, irrespective of the fact that they pay smaller amounts to the same account every month. It was a pain, but I think a worthwhile one.
My late father was scammed years ago - in a complex scam at the time which took account of him calling the bank back and then disabling his phone line so the bank couldn't contact him. The bank refunded him fifty grand or so... (we implemented a new protocol where he would call someone he knew, like me, in future similar events).