I’m from northern Europe, and I have never heard of or met anyone that preferred bank transfers ever. If I can’t pay online with credit/debit card, I’m not buying from there, but it’s extremely rare to find somewhere that does bank transfers for B2C at all IME.
Isn’t Klarna a credit service more like a loan where you then distribute the payments over the next few months? You sign a contract and stuff just like bank loans, it’s not the same as making a bank transfer at all.