It really depends on management style.
In democratic management styles, then what you said is correct. The manager is just a conduit for information.
But in authoritarian management or top down management, which is having an alpha male (or female) with a lot of talent and ego calling the shots and making the big decisions really works well when it works (and fails catastrophically when it fails). In this style of management, professional skills in whatever it is that the team is doing, which means technical skills in development teams, towers above management or interpersonal skills in important towards the success or failure of the team. Someone with good technical skills tends to make good decisions and someone with bad technical skills makes bad decisions. You cannot build success around bad decisions. Beyond that, the only thing really useful is a bit of charisma to keep the team happy and the ability to get most of one's meaning across. Mostly one just has to be 70% understood anyway, since a bit more latitude in interpreting orders is only going to be a good thing in giving workers room to move.
I've found, especially in Asia where a more paternalistic style is favoured, the outcome of a project is especially determined by the technical skills of a manager and little else. Guys who get into little fights, throw temper tantrums and rarely get their meaning across, but make good decisions tend to have better success than good communicators who don't quite understand the problem at hand.