I think it's just the combination of a direct match in a subdomain name, the popular and widely linked to domain name, and lack of any other context in query.

I don't remember whether DDG does anything to the scores it gets from Bing. They might, but then - taking into account how particular its users are... - the poor Franz K. would be on the third page, far behind even a Kafka library for Franz Lisp. (No, that's not a thing. A shame, I know.)