It might not be easy to break through, but once you can get him to reflect on his management style, growth can occur. You may have to be forceful about it, and make sure that he knows that figuring this out is a basic expectation you have for him.
Take a moment to look in the mirror yourself. It’s easy to lead good managers. How well have you done with coaching and mentoring him? If you have been expecting him to just figure it out, then you’ve modeled the very behavior you’re concerned about.
Now, consider the resources you have at your disposal for turning the situation around.
Your best asset is your willingness to be transparent with him. Set up time to talk about the issues in a reflective and nonjudgmental way.
Help him analyze the team to figure out specific actions that would help. Maybe one person needs some skills training and someone else needs to work on their communication skills.
Then support him while he determines steps that could help them progress. Just don’t fall into the trap of telling him how to move forward.
If he keeps coming back to you for advice, insist that he come back with solutions. Then treat his ideas as valid starting points, asking probing questions to help solidify his ideas.
Look into training options for him. If you work in a larger company, your human resources department may have management skills programs or a budget so he can get training externally.
Also tap into your manager corps. Mentoring a struggling manager could be a good development opportunity for one of your strong leaders.
Set up structure to keep him on track. Use your regular one-on-one meetings to talk about his management goals. If you don’t have regular meetings, that’s a red flag for you.
If he is open to growth, these steps should help. Ideally he will embrace this process.
On the other hand, if he resists, consider whether he really is suited to his role and act accordingly.