So before I worked at the last job, I worked for a camera store back in the last days where those were still generally a thing (2004-2010 - it wasn't too bad of a job for a kid in school). We offered by now, pay later back then, and I don't think we invented it either. Of course it was basically just a credit card application, and there was no requirement to pay it off within a set amount of time, but if you didn't, then they'd hit you with all the interest that had quietly been accruing during their "introductory period" or whatever they called it. Which is to say that it was scummy and deceptive, but not much more so than other American business practices and certainly less than others, and hey they had to make money and eat too.
Perhaps Klarna really is better, but then again maybe that's why they're hemorrhaging money at such an impressive rate.
I know PayPal "Buy-in-4" has no interest or late fees in its terms. So in that regard, it really is a 0-interest loan, paid in 4 installments. I haven't looked into Klarna, but there's an NPR Planet Money podcast about these types of schemes. The profits are made up by the fact that demand increases compared to credit cards (many are ineligible for credit cards, or don't use them for whichever reason), and that the merchant is charged a higher rate by the BNPL company.
Perhaps Klarna really is better, but then again maybe that's why they're hemorrhaging money at such an impressive rate.