Complex sentence: At the end of the century, the increasingly radical political environment created in large part by the French Revolution lead to the tightening of governmental restriction and the decline of the debating societies, and they virtually disappeared by the beginning of the nineteenth century.
Split into simpler sentences: At the end of the century, the political environment created by the French Revolution led to the tightening of governmental restrictions. The debating societies declined, and they virtually disappeared by the beginning of the nineteenth century.