Answer:
The delegates decided to write a new Constitution for a couple of reasons. The convention started because of Shay's Rebellion. The original purpose of the Convention was to revise the Articles of Confederation. Some delegates disagreed saying that revising the Articles of Confederation would not improve the government because it was too weak so they needed to create a new, strong government. The Article of Confederation exposed all the weaknesses of the government and this was caused because of the limited powers and they had no national government. There were two sides that agreed with the new document. The federalist and anti federalists.
(sorry, I know this is poorly written and organized and sorry if I repeated anything)