Microsoft Project Manager interview questions

The process itself was very slick, professional and (seemingly) friendly. A written set of questions, interview with a senior in the same role, then another interview with hiring managers. Feedback throughout was quick, and positive. Until the final decision - then ghosted, no explanations or even a one line email just an auto notification. Don’t give good feedback at each stage and then no explanation at the end. How can people learn from mistakes or gain experience for next time?