The interviewers were friendly and asked a lot of questions about my experience in a small Architectural Design firm. They also asked me to see what I had worked on during Uni and the designs I produced at the firm. I thought the interview had gone well because they did seem quite interested.
The rejection email came after several weeks and did not specify a reason for my rejection. The little feedback I received after I asked was also quite unclear and not very constructive.
They said that they were looking for someone with a more "linear" design education. I assume this meant they did not like that I had pursued a course in graphic design and was temporarily freelancing as a graphic designer. My only guess was that they didn't like to hire candidates that might a bit different from themselves.