Being a good sales person does not make you a good manager. The peter principle is as real as lawrence pPeter said it was, and i'm editorializing here. It would also seem to be incredibly stupid. If the firm's only goal were to have the best possible managers than the firm could by putting more weight on collaboration experience and less weight on sales numbers,. raise overall firm sales numbers by about 30 %.
People who are good at their jobs routinely get promoted into bigger jobs they’re bad at. We explain why firms keep producing incompetent managers — and why that’s unlikely to change.