Microsoft Software Engineer interview questions

I went through all the interviews (4 steps) and I didn't leave any questions without answer and my codes and designs worked. But the comment I got was "your background is more in data science and software engineering is not a good choice for you". Ok‌, but then why you did that to me?!

1 phone screen: some basic probabilities questions and small system design: how to design a high concurrency situation 2 round technical round: leetcode medium + projects: dive into some technical questions related to my resume + behaviour questions: what's the biggest challengage you ever met