You're a super strong candidate and have an impressive profile. Wish I had your academic pedigree.
I got rejected from MC-MPA despite .... and rejection hurts. Really painful. Like you, asking questions, pondering, and wondering why. Truth be told, it's never one thing -- a bunch of factors, some out of our control -- come together to produce disappointing outcomes and results.
We'll fall short and even fail in leadership tests throughout life and while this is very difficult to accept, this experience will undoubtedly make you a stronger leader if you can show grit and move past it. I hope to do the same. Wish you all the best.