Why did the framers decide only 9 of 13 states would need to ratify the constitution rather than 13 of 13 needed for the articles of confedertation

Understand first that after independence and before the Articles Of Confederation the only thing that the 13 former colonies had in common was that they were former colonies of Great Britain and the only reason for their unification during the revolution was to focus the fighting forces as close to a singe unit as possible.

Because there were not allow