Graphcore Full Stack Applications Developer interview questions

First I had a chat with the hiring manager which went well. Then I was given a HackerRank exercise with no time limit which was possibly the easiest problem I have ever had to solve for an interview (a Python application to parse some Strings). Then I had to wait almost a month for a response due to some project deadline (despite this being such a small exercise to mark). When I did get a response I was told that although my solution was good, someone else had scored higher so I would not advance to the next stage. I couldn't understand how anyone could make such a simple program better and also I couldn't understand why only one person could go to the next stage.