Every poor manager I’ve ever dealt with has been a poor communicator. Almost every shortcoming or problem I’ve seen people have with a manager or coworker could be filed under a problem with communication. It’s THE thing in the workplace. Ideas, expectations, priorities, and everything else in the workplace come down to the ability to communicate. If you cannot communicate clearly, you are lost, and the people who work for you or lost.
Yet how many organizations promote the top performer or their most senior individual contributor without ever considering whether they are good communicators? And how many prioritize teaching them how to communicate as managers?