Coursera Senior Front End Developer interview questions

Got reached by a recruiter and online and was scheduled for a 15min intro call, then for a 45min pair programming session. I came up with a solution relatively fast (including test cases) and discussed a lot of design-related issues. The interviewer seemed very satisfied and he actually told me that the recruiter would get in touch same day / next day to setup the next steps, however I got a rejection email without an explanation a couple of days later. I guess the position was filled, but I don't really know why. Overall I found the 1st round interview to be quite simple. All communication was very professional.