Zheo - not all monks are Crahn Sect members or believers, although I dare say persecution under the early days of City Admin lead to many more turning that way. The reason for the dome attacking NC after the Ceres was has never been clear. However, the simple answer to your last question is that there simply aren't any. After CA detonated the Dome's own weapon within the dome, the vast majority of the populace was killed or dieing. Those that survived wre certainly in no position to fend off the hordes of anti-city alliance forces pouring into the dome via the DoY tunnels.