The leftover syndrome
I'm simply baffled by how often I meet the following attitude concerning skills requirements for a project manager: "Well, you obviously don't have any of this organization's core skills, but you are employed here so you must be a project manager".
Of course, this is usually not said out loud, but the thinking is written on everyone's forehead.
When you take into account that these organizations often rely on methodologies where the project manager is the single most important person in a project, this reasoning becomes even harder to understand.
Still, the hard facts are there. You have a project team with some people having the required core skills and a project manager without training in either the core skills or in project management.
And then people are surprised when the project starts to slip.