The Articles of Confederation contained several weaknesses, why would the United States purposefully create a weak government under the Articles?

A great deal of the problems that the colonists saw in the rule of the British in the Revolutionary era boiled down to a misuse or abuse of power by King George III and Parliament. The government of the United States was meant to be relatively weak by design, to prevent similar abuses of power. (Under the Articles, the government had no power TO abuse!)

The other piece to remember is that the colonies each had developed rather differently and, much before the French-Indian War in the mid 1750s to 1763, they had little to do with one another. The French and Indian War brought along the first notion of uniting. The problems with the British spurred that notion along.

That, however, does not mean that the people of the colonies, and then the States, thought of themselves primarily as one big united group. The Confederation was designed as an alliance among the states – not a powerful government to lead a union – and that alliance was mostly in place in case the British had designs on reclaiming her lost territories.