The members of the third estate did indeed form the National Assembly in response to feeling marginalized and frustrated with the actions of the king, including his proposed new tax on land. The members of the third estate, who represented the common people and bourgeoisie, felt that they were not being fairly represented in decision-making processes and that their grievances were not being addressed. As a result, they took matters into their own hands and formed the National Assembly in order to advocate for their rights and interests. This eventually led to the French Revolution and the overthrow of the monarchy.
