If the previous government had been overthrown and a major reform which can be recorded in history books had been accomplished, the overthrown government must have had political power and must have maintained a political system over a long period of time before that.
もし既存の権力を倒して史書に記すような政治の大改革を行ったのであれば、倒された権力は、それ以前長期に亘り権力を掌握し、政治体制を維持してきた者でなければならない。