Bell Rotational Leadership Program interview questions

I went to Bell's info session on campus and applied directly on their website. I was notified with a phone interview soon after. The phone interview went very well and consisted of fir questions and some general questions about leadership and communication. In the following day I was informed of a second round 1:1 interview on campus. The interview was much harder than the phone interview. It came with many specific behaviour questions, such as "Tell me a time when you thought you were doing the right thing but made a big mistake instead". The good thing is the interviewer was very nice and friendly, and I took the lead in the conversation several times during the interview. The process is really as I was noticed with a last round presentation interview soon after. I was given a HBS (later I found out they actually gave the same case to all the candidates) to me and I had 2 hours to go through the case and prepare a 25 minute powerpoint presentation. They asked me many questions during the presentation, and I was very nervous since this was my first presentation interview. I received an email 3 weeks after saying I was rejected.