Question

Why was the battle of Yorktown sucessful?

Answer 1

The significance of the conflict was that Cornwallis surrendered to George Washington as French and American forces trapped the British at Yorktown. 
Hope This helps!!

Answer 2

http://www.history.com/this-day-in-history/battle-of-yorktown-begins

" Peace negotiations began in 1782, and on September 3, 1783, the Treaty of Paris was signed, formally recognizing the United States as a free and independent nation after eight years of war."

Yes, it was successful.