It took a while here, too
From this timeline of our own Revolutionary War era (163-1789) by North Park University:
1781: British surrender at Yorktown.
1783: Treaty of Peace is signed.
1785: Land Ordinance of 1785.
1787: Constitutional Convention in Philadelphia.
The Constitution didn't become effective until 1789, some 8 years after the British surrender at Yorktown. These things take time.
