Why were the articles of confederation replaced with the constitution?

The significant downfall of the Articles of Confederation was solely its weakness. The national government, under the Articles, was inadequate to strengthen their policies and hence had no power transmitting most of the power to the state governments

The need for a powerful Federal government soon became obvious and ultimately led to the Constitutional Convention in 1787. The contemporary United States Constitution superseded the Articles of Confederation on March 4, 1789.

classical republicanism, also known as civic humanism, is a form of republicanism  developed in the renaissance inspired by the governmental forms and writings of  classical  antiquity, especially such  classical  writers as aristotle, polybius, and cicero.