Final answer:
The cause of the radicals and sans-culottes gaining power in France was a combination of economic woes, social unrest, and political discontent.
Step-by-step explanation:
The economic crisis, with rising food prices and widespread poverty, led to mass dissatisfaction among the lower and working classes. The sans-culottes, who were unable to afford the fashionable culottes worn by the aristocracy, became a symbol of the wealth inequality and sparked revolutionary fervor. The radicals, such as the Jacobins, emerged as a political force advocating for the complete elimination of the monarchy.