Why did the founders replace the articles of confederation?

The US did not have an actual national government under the Articles, which retained the sovereignty of the states and required them to cooperate in practically every aspect. This was always difficult and sometimes impossible. There was no executive except the President of Congress, no standing military, and no unified system of courts. The framers decided that the nation needed a stronger unifying force, and the weaknesses of the Articles had already vexed them for more than 7 years.