When a second body shows up in another home, Aurora realizes there's more to the murders than she thought.
Not wanting to be a spectator in what he viewed as a dereliction of duty and criminal action by Starfleet, Picard gave Starfleet a choice of either accepting his revised plan for the mission, or his resignation, in which chose the latter.
Many Romulans feared even expressing dissenting opinions in order to not bring the attention of the Tal Shiar.