The correct answer to this open question is the following.
You did not include the link to the video. However, we can answer in general historical terms.
After the battles of Concord and Lexington, which represented the beginning of the American Revolutionary War in April 1775, John Adams discussed the situation with other Patriots. They expressed logical arguments about the real chances the colonies had to defeat the British troops, but they also added some persuasive arguments in their debates with the delegates.
Finally, they decided that the Continental Army needed a strong leader as its Commander. That man was General George Washington.
DIscussion and arguments continued after English King George III accused the colonists of treason. That is why John Adams supported the idea of having a formal declaration. He asked Thomas Jefferson to draft the Declaration of Independence and it was ready to be promulgated on July 4, 1776.
