Why did the Founding Fathers choose federalism?

The founding fathers realized that by 1789 the Articles of
Confederation (ratified in 1781) was putting the new nation in critical danger. As a
constitutional structure, the Articles served as a loose union between the different
states and a centralized national government. Unfortunately, the states were so
distrustful of a centralized authority, the national government was extremely limited in
its capacity to govern. Although the national government could make war and negotiate
treaties, it lacked the fundamental power to tax. Without the 'power of the purse' the
national government was essentially held captive by the individual state governments. In
addition, the powers the national government did have were impossible to enforce leaving
the national government again at the whim of the states. Furthermore, Shay's Rebellion
caused the founding fathers to take the weaknesses of the Articles seriously. In 1787
the Constitutional Convention assembled for the purpose of revising the Articles.
Instead they constructed a new document; The U.S. Constitution based upon several
principles one of which was Federalism. Federalism redefined their confederation by
creating a fedeal union. A federal union is a compromise between a unitary system's
concentration of power and a decentralized confederation of state
structure.