The promotion to the managerial job position is always a challenge, both for the new manager and the subordinates.
The new manager has no experience with the management and leadership, just has the experience, how he or she was managed. The previous manager always build the basic pattern for the behavior of the new manager.
As the new manager wants to be successful right in the beginning, he or she starts to act quickly with no clear vision and goals in mind. When the new manager is not coached and mentored by the senior manager, he or she makes many faults. When he or she is lucky, some of the subordinates have courage enough to provide the useful feedback.
Otherwise, you have to be patent ... the new manager will learn, how to manage the team of former colleagues.