Why was France de-Christianized during the French Revolution?

The Catholic Church was damaged but not destroyed as a political and economic force during the French Revolution. Church property, monasteries and convents were appropriated by the state. The tithe was ended and priests were required to take an oath of allegiance to the Nation or to leave the country. There were many priests who were slaughtered and it was not until 1801 that Napoleon reached a Concordat with the Pope. He restored Church authority over matters of faith but he did not return Church Property.

In defense of the French Government, the Ancient Regime had allowed the Catholic Church to become the largest land owner in the Nation and it controlled no less than 10% of the nation's wealth, paid no taxes and received a tithe from everyone in the Third Estate. It exploited, was inefficient and corrupt.