Speaking as someone who, when I was a junior, only ever worked for first time managers -- I hated it, and wished that I had a more experienced manager. Meanwhile, my senior friends who had a first time manager enjoyed the process of teaching a new manager the ropes.
When I was six months into the job I certainly didn't know how the org functioned, nor did I have any political capital to move things my way.
I always suggest folk to embrace and understand an existing organization's culture before attempting to effect change within it.
This happened to me too. I didn't picture myself as a manager and I thought I wasn't legitimate to lead the team, being less experienced. But it turned out my team members were quite introverted and none of them wanted to take that role. In the end, it was a fruitful collaboration and a very good experience. I never saw that position as hierarchical, more of a different role within the team.
Perhaps that's why these seniors are being managed by someone with less experience?
Guess it depends on the team concerned.