I interpreted more as 1, he wanted the interim choice to be someone disinterested in the permanent position so that the interim wouldn't have unfair advantage against other candidates and 2, he wanted someone outside the department so that the inevitable multiple candidates applying from the inside would not view the interim as having unfair advantage. I don't think this is a solid indicator the next Chief will definitely be an inside candidate.
I interpreted more as 1, he wanted the interim choice to be someone disinterested in the permanent position so that the interim wouldn't have unfair advantage against other candidates and 2, he wanted someone outside the department so that the inevitable multiple candidates applying from the inside would not view the interim as having unfair advantage. I don't think this is a solid indicator the next Chief will definitely be an inside candidate.