Was the biggest issue just the micromanaging?

I've seen this several times when newly promoted managers are given 1 or 2 reports. Specifically individuals that are high conscientiousness, i.e. hard working, detail oriented, organized. Then they are promoted, and put into stressful position where there previous strengths can become liabilities and they spend all there time making sure their reports do the job in the same way they would have done it. And if they had more reports it would quickly break them of this micromanaging habit because they just don't have the time.

I found that more relaxed/laid back managers tend to do better with a 1-2 reports but then quickly start to run into issues as the team size grows and overwhelms their organizational abilities.