Klarna is successful for a few reasons. First, it's very convenient for customers. They can finance their purchases and spread the cost over time without worrying about interest or fees. Second, it's straightforward to use. Customers can sign up for an account and start using Klarna with a few clicks. Finally, Klarna is very popular with retailers. It's partnered with over 200,000 stores worldwide, so customers have plenty of options when it comes to where they can use Klarna.