Unfortunately, they're huge, and I doubt the Swedish authorities will do more than give them a fine and a slap on the wrist.
Here in Finland, It's not uncommon to have no debt apart from the mortage on one's home.
Debit card payments are not debt - they're effectively the same as a direct transfer from the user's bank account.
I'm very conflicted about Klarna - on the one hand they do present an easy and (usually) safe way to handle transactions with small retailers to whom I don't necessarily want to share my payment details.
But on the other hand, they use a variety of dark patterns to try to get you to pay: 1. on credit 2. by signing-up for their credit-card
One unfortunate part of their earlier history, was that when you promised to pay with Klarna on a website, and was told you'd receive the invoice, there was a (perceived?) tendency for that invoice to never be sent due to an 'oversight'. When this happens in Sweden, the buyer gets a reminder a few days after the due-date, with a pretty large extra amount to pay.
There were quite a few stories about this in the press at various times [0], and I know quite a few people from Klarna and would tease them about it - which they always strenuously denied - but then it happened to me.
In any case, finding out how this happened is going to be interesting.
[0] in Swedish: https://www.svd.se/mangder-av-klagomal-mot-klarnas-fakturor
DeepL translation: "Lots of complaints against Klarna invoices. Klarna, the high-profile IT company, is being criticised by a host of customers. Many say they receive invoices with reminder fees and collection demands directly, without having been reached by an original invoice. The Swedish Consumer Agency is critical of Klarna's invoicing methods for several reasons and is currently investigating whether the company is behaving legally."
Translated with www.DeepL.com/Translator
I use them because consumer protections with other methods aren't as good here in the States. Paying with a credit card, if I have an issue with a vendor, after a good faith effort on my part to resolve the issue, I can just ask the credit card company to deal with it. (I don't abuse this, but I don't doubt there are people who do.)
There are better and worse credit card companies for this. American Express has great customer service but they aren't accepted in as many places.