One of the chief complaints about the Articles of Confederation was the limitations of the document. The national government created by the Articles was too weak and left little power to the federal government to enforce its laws on the states or even collect taxes.
So when the Constitutional Convention reconvened to create a better Constitution, the framers made sure to create a much stronger federal government, one that could make necessary new laws and enforce them, conduct foreign relations, and even collect taxes.
Now the original Constitution was not without flaws--but thankfully, additions could be made to the document in the form of amendments. The first ten amendments became known as The Bill of Rights. Much later, other important amendments were added like the Thirteenth Amendment, which abolished slavery.