The same thing happens in business, where somebody will be promoted into a managerial position because they are good at the job (in this case this would be playing football) BUT the skill of managing is a completely different beast and there is no guarantee being good at a job translates at all to management. Being able to relate to the players is one thing but you don’t have needed to have played extensively at the highest level to understand that I don’t believe.
First and foremost the candidate should be the best MANAGER of people, players, and tactics of which I don’t believe any of the recent English top professionals are at all despite their great careers. The manager doesn’t need to run around and kick a ball