What made that one PM great? What did they do or what was their philosophy? The outcome was that they got the team to be more productive, but what was the input that differed from the other PMs?
I can't really say. I'll describe some of the things I observed: they had incredibly good people skills with both customers and coworkers, they had the ability to ask incisive questions, and make good decisions with imperfect information, they context switched smoothly, they were well organized, and they made people excited about what they were working on. They also worked longer hours than anyone I know of at the company.
This sounds like a combination of charisma, leadership, and drive, which makes sense as a pretty rare set of qualities for one person to have.
... And reading that, I think I left out that they were super nice, and everybody liked them.
