Once upon a time, a long time ago, in a country named France, there were some people called Christians. They believed in a very special person named Jesus and followed his teachings.
Then, there was a big revolution where people were upset with the king and wanted to change the way things were done. These people were called revolutionaries.
The revolutionaries thought that the Christians were too powerful and didn't like the way they were doing things. So, they decided to stop the Christians from having too much influence. They called this process "dechristianisation."
The revolutionaries took away some of the Christian symbols and replaced them with new ones that didn't have anything to do with Christianity. They also started treating Christians badly, making fun of them and attacking their churches.
The revolutionaries wanted everyone to believe the same things, and they didn't want the Christians to be in charge anymore. This made some Christians very upset, but others agreed with the revolutionaries and went along with the changes.
In the end, the dechristianisation of France was a big deal and changed the country in many ways. It was a very complicated process, but the main idea was that the revolutionaries didn't want the Christians to have as much power as they had before.