“I’ll just do it myself.”
This is a common refrain among managers, whether directly stated or inferred. It’s more common with newer managers and micromanagers for essentially the same reason: by the time I explain exactly what I need, I could have done it myself.
The new manager is fearful that the project won’t be done correctly, while the micromanager thinks that no one can do it as well as she can.
Regardless of the reason, the outcome is the same. When you do it yourself instead of delegating to a team member, over the long term it will backfire on you.