Why was a weak national government created under the Articles of Confederation

The articles gave the government no separation of powers. The government was too weak, the Articles left much of the power to the states (if I remember correctly, states basically went by their own state constitution). Congress didn't have the power to tax. To change the Articles, it had to be decided unanimously by all states. Also, 9 out of the 13 states had to approve any major law before it was passed and Congress couldn't regulate commerce. There was no president to lead, no established court system, and every state had only one vote in congress. Basically, the articles created no separate executive department to carry out and enforce the acts of Congress and no national court system to interpret the meaning of laws.