Why did the framers include the necessary and proper clause in the constitution?

The answer is:

For two purposes.

1-  to facilitate organization of the government, such as empowering Congress to organize the judicial branch.

2- to help effectuate the other enumerated powers of Congress.

Explanation:

"The Congress shall have Power To ...make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of the United States, or in any Department or Officer thereof".

why was the national assembly formed by the third estate?

the estates-general had not been assembled since 1614, and its deputies drew up long lists of grievances and called for sweeping political and social reforms. the third estate, which had the most representatives, declared itself the national assembly and took an oath to force a new constitution on the king.