>>/45131/
A revolution is a complete rupture, they cut off all the ties to the previous system, but they still have the need to be legitimized. This legitimization is the source of their power, the reason why they are the ones holding the reins.
For the classical revolutions of the enlightenment it was easy. The previous monarchies they toppled, the absolutist autocracies ruled by the grace of God, the source of the power was God. The revolutions said, the word of the people is the word of God, and they claimed they represent the people, the source of their power is the will of the people.
But what if both the new and the previous regime holds the opinion that the source of power is the people (because that is the prevailing school of thought in that era, or simply that is the fashionable thing to say)? Well, they just have to claim they represent the people.
Now that is ok, but there was a practice already in place which was supposedly served the people to declare its will. It is a democracy (a version of it, usually some bastardized one), the elections, where people chose the governing group. So the new guys have to claim that the previous regime wanted to abuse that practice, wanted to eradicate it, which made them lose the trust of the people. They also have to say they couldn't take the road of that practice, so had to use the revolution to set things right.