Resolution interview questions

I had 3 rounds of interview to join the paid media team. The first round was to get acquainted with the HR which went well. The next round was with 2 directors who asked about my experience which also went well and set up for the third round involving an assignment. I ensured to be as detailed with it based on the brief and they said it was more than what they expected. I assumed it was a good thing given my experience and skills were well above their requirements for the role. I had experience for a director role but they were of the opinion that a manager would be better suited to which I was also open. Even then they could not offer me the job and only said that another candidate with more experience on a similar client was chosen. They also said all the other roles were not available. This seemed a bit strange considering they were actively looking out for many managers.