Why did the federalists believe that the constitution would prevent the national government from gaining to much power ?

The government was divided into three branches, judicial, legislative, and executive.  The federalist believed that the national government should take care of everything and have the ultimate authority, but the constitution limited what the branches could do, therefore, the federalist believed that the constitution gave the national government too much power. The Anti-Federalist argued that the constitution gave too much power to the federal government. The Federalist believed that the nation might not survive without the passing of the constitution, and that a stronger national government was necessary after the Articles of Confederation failed.

No we should just pass