What are the reasons for the terror during the Great French Revolution?

Initially, the terror in the country began because the new government tried to punish those whose blood the people thirsted for (first of all, they were members of the royal family). However, in the future, the revolutionaries began to fear for their position in power, so gradually those who were initially on the side of the revolution began to enter the ranks of the executed. So executions became a weapon against politically objectionable figures. Because of this, the terror acquired a huge scale, a large number of innocent people died.