I think you owe it to yourself and they owe to you a debt of professional courtesy the explanation of what led them to the decision. In a situation like that, it's best to ask, be vulnerable, consider the merit of their observations and learn from them. They may hold back due to legal issues but you at least should ask.
There could be a lot of reasons but it's best not to burn cycles on “what if” – ask and find out (call beats email in this case). Else reflect, learn, grow, repeat. In that next role, be a differentiator – be someone who tries harder, looks for better methods, excels. Some companies hate that too! Things like this can be a blessing in disguise. Don't ask “what if I fail” – ask “what if I succeed”.
I'm much later in my career and just getting to the cpa world but have seen much of this first hand.
AUD - 77
BEC - 81
FAR - 77
REG - 81
REG - 1.
Becker only - fail (forgot to study depr - oops); 2. Becker only - Pass
FAR - 1. Becker only - fail; 2. added
Ninja Notes and MCQ - Pass
AUD - 1. Becker videos; Ninja Notes, Audio, MCQ, Becker
Notes - Pass
BEC - 1. Ninja Notes, Audio, MCQ, Becker Notes - Pass