Is the pecking order really important at work?

In 2018 I hired a director of operations to run our company. He had been interviewed by the team. We had a team that worked very well together and I jealously guarded that. I did not want anyone disrupting the manner in which they worked.
Within 40 days of the new manager coming on board, team members had either been fired or had quit. What went wrong?
I listened to this Ted Talks video and I learnt something from it. It is about chickens, but it is super instructive. I hope you can apply some of what she says to your business.