I’ve literally never seen this happen in the tech world
Well, as soon as HRBP found out I would become a EM, suddenly there were 2 other areas that needed EMs much more than our team. (As we were very functional).
I made a condition that I would become EM only for our team and did not desire to lead others I didn't know.
Given two EMs, one that came organically from a team and another that came "from the outside" and spent a few months working with a team - what advantages and disadvantages would the first EM have over the second?
I will say that for very dysfunctional teams it could be valuable to get an outside perspective which can do more severe change but hopefully this is less common.