League Senior Software Engineer, Backend interview questions

Recruiter contacted me on LinkedIn. Then I quickly got a call from League HR, this first interview was fairly easy, the recruiter describes the company, and you talk about your motivation and why you would like to join League. Then I received a take home coding challenge in Golang. I liked the coding exercise, it involves building a backend API with Unit Testing. League reviewed my code in two days, and I got invited to the next stage for on-site interviews. I had two interviews, the first one, was a technical interview where I chat with 2 senior engineers about my experiences and I go in depth about my technical experiences. The last interview was a system design interview with 3 very young engineers. I was interviewed by 2 junior engineers (less than 2 years of exp) and 1 senior engineer (with less than 4 years of exp). After one week of waiting without any feedback I e-mail the HR, they told me I got declined and they don't disclose the reason.