You promote your strongest individual contributor and, three months in, both of you are frustrated. This is not a hiring mistake — it is a predictable trap. The skills that made them excellent are not the skills the new role rewards.
Great contributors are wired to do the work. Great managers are wired to create the conditions for others to do the work. That is a near-total inversion of where their attention and self-worth have lived.
Without support, the new manager reverts to what they know: they out-work the team, hoard the interesting problems, and call it leadership. The team learns to wait for them.
Coaching breaks the loop early. It gives the first-time manager a place to practise the unfamiliar moves — delegating, giving feedback, sitting with the discomfort of not being the one with the answer — before those habits calcify.